I’ve seen the future of America, and it’s the University of Houston.

Houston, Texas, is an immense immigration magnet, and its big public school is one of America’s great institutions of integration and upward mobility. UH is by one measure the second most diverse public research university in the country. What that means is that the primordial black-white American racial dynamic doesn’t really exist there.

Houston doesn’t have "Asian" students. It has students of Vietnamese, Korean, Chinese, Indian, and Indonesian ancestry. Lots of them. There are plenty of African Americans, but also plenty of Nigerian Americans. One sees young women in a variety of fashionable headscarves. When I finished my MFA there in 2015, whites were still the largest group on campus, edging out Hispanics, 27.6 to 27.5 percent.

The University of Houston is a pretty good preview of what America is going to look like within my toddler son’s lifetime. A lot of Americans —especially older white ones — are pretty freaked out about this.

In an interview with the Canadian Broadcasting Company, Ed Hunter, a 50-something Maryland construction worker and Donald Trump enthusiast, summed up the anxiety of many older white folks in six pithy words: "The American people are being replaced." The "American people," Hunter maintains, "don’t want to be fighting off hordes and hordes of people from foreign cultures that are utterly changing their country to the core."

For Americans like Hunter, to "make America great again" is to defend a certain idea of American national identity — an idea of what this country is at its core. And that means making sure that America doesn’t become what the University of Houston already is. But no matter who wins the election this November, Hunter has already lost. It’s too late.

American national identity has already changed, and there’s no going back

The Census Bureau projects that whites will cease to be a majority of the population around 2045 — about 30 years from now. This eventuality is baked into the demographic cake. In 10 years, by the time my toddler is in middle school, white kids will be less than half of the under-18 population.

And unless the United States sees an unlikely influx of white immigrants (for every European who became an American legal permanent resident in 2014, there was an African, 1.5 Mexicans, and four Asians), or white birthrates rise above replacement level, even the absolute size of the white population is likely to shrink. Add to all this a happy increase in interracial marriage, and you have all the ingredients for what resurgent white supremacists ridiculously and self-pityingly call "white genocide."

To many older Americans, authentic American identity is Christian as well as white, and white Christians have already fallen into the minority – no demographic projections necessary. Non-Hispanic white Christians now make up just 45 percent of the American population — down from 54 percent just eight years ago.

In his recently published book The End of White Christian America, Robert Jones, head of the Public Religion Research Institute, observes that the fading dominance of white Christianity at the core of American culture isn’t simply a demographic change caused by immigration and differential birthrates. It’s also a consequence of a decline in religious commitment, especially among white millennials. Religious people tend to have more children, so secularization and demographic change are related: That white millennials are losing their religion helps explain why they’re unlikely to have enough kids to replace themselves.

"[W]hile the country’s shifting racial dynamics are certainly a source of apprehension for many white Americans," Jones has said, "it is the disappearance of White Christian America that is driving their strong, sometimes apocalyptic reactions. Falling numbers and the marginalization of a once-dominant racial and religious identity — one that has been central not just to white Christians themselves but to the national mythos — threatens white Christians’ understanding of America itself."

This sort of momentous cultural change threatens white Christians’ understanding of what it means to be an American because what it means to be an American has actually changed. Trumpism looks like white identity politics rather than just regular old American politics that happens to be dominated by an entitled white majority, precisely because traditional white identity has already moved out of the core of American national identity.

Many white Americans, Jones says, are in the process of grieving this fact, and that helps explain the contours of this year’s election. The first stage of grief is denial. The second is anger.

America’s new national identity is a triumph of capitalism over cultural control

It’s worth emphasizing that certain racial and religious aspects of American national identity can move toward the margins of the culture without anyone doing the marginalizing. Nobody caused secularization, for example. It’s happening in all wealthy, liberal-democratic countries. The needs served by religious belief and participation seem to weaken as people become more prosperous and oriented toward individual self-realization. This is not to say the evolution of what it means to be an American doesn’t reflect some policy choices. Of course it does.

Americans have always been worried about letting in the wrong sort. As Aristide Zolberg emphasized in A Nation by Design: Immigration Policy in the Fashioning of America, the United States has always rigged immigration and citizenship policy on the basis of ideas about which of the world’s people were and were not well-suited to the American way of life. Benjamin Franklin and Thomas Jefferson worried a lot that the non-English just didn’t love republican self-government enough to sustain the distinctive freedoms of a brutal colonial slave state.

But the project of fashioning an ethnoreligious American identity has always been in conflict with a dominant and defining American impulse: to get rich. The United States has always been a distinctly commercial republic with expansionary, imperial impulses. High demand for workers and settlers led early on to a variegated population that encouraged the idea, largely traceable to Tom Paine, that American national identity is civic and ideological rather than racial and ethnic.

The idea that Americanness is based on belief and not blood has always been inviting, and helped supply the young, westward-expanding commercial republic with the people it needed to grow economically and territorially in a way that made inclusion and assimilation possible, if not painless. The American ruling elite has always been picky about who got in. But they’ve always prioritized money and power over WASP dominance; given their nation-building ambitions, they could never be as picky as they might have liked.

The satisfaction of capitalist impulses has always led to a more diverse and multicultural America. And this has been met time and again with the reassertion of nativist worries about which of Earth’s peoples are racially and culturally fit to honor and live according to the American creed.

For example, Chinese workers were brought in to build the railroads, then explicitly barred by the 1882 Chinese Exclusion Act. And the Ellis Island­–era surge was met with the Immigration Act of 1924, enacted during the high tide of Progressive Era scientific racism. The law set quotas on immigration from any given country at 2 percent of the number of American residents who were born in that country in the 1890 census. (Surprisingly, by today's standards, immigrants from Latin America were not covered, as they were not yet considered a "threat.")

By using the immigrant mix of 1890 as a baseline, the 1924 law effectively closed the gates of the United States to almost everyone outside the Western Hemisphere except for Northern and Central Europeans.

Agricultural labor shortages led to official guest-worker programs for Mexican workers in the 1940s and '50s, which permanently altered the ethnic mix in the burgeoning American Southwest. And then we got "Operation Wetback" to try to put the genie we’d summoned back in the bottle.

The 1965 Immigration and Nationality Act, which went into effect in 1968, was a political choice that broke decisively with America’s four-decade era of highly restricted, explicitly racist immigration policy. But it certainly wasn’t a plan to create the University of Houston’s current student body. Nobody expected it to have the effect that it did.

In some ways, this stuttering, schizophrenic pattern in immigration policy may — ironically — have deepened America’s sense of itself as an exceptional "nation of immigrants." There’s a case to be made that the slowdown in immigration from the 1920s through the '60s made the absorption and integration of Ellis Island–era immigrants easier, heightening American confidence in its exceptional capacity for assimilation.

The 1965 immigration law, in the spirit of the era’s landmark egalitarian civil rights legislation, greatly expanded national quotas, added hemispheric caps, and favored high-skilled immigrants and family reunification. The supporters of the bill, including President Lyndon Johnson, expected mainly Europeans, whose economies were still struggling to bounce back from the war, to take advantage of a newly open America’s booming economy. But that’s not what happened.

The family reunification exemption from the hemispheric caps led to a huge, unanticipated surge in Mexican immigration. Moreover, doing away with the old racial quotas, in combination with Cold War–era refugee policy, led to waves of immigration from Asia and Africa that no one expected in 1965.

Consider how my hometown, Marshalltown, Iowa, has been transformed. In early 1980s, when my family hosted a family of refugees displaced by the Vietnam War, there were maybe three or four Hispanic families in town. Today, Marshalltown’s population is about 25 percent Hispanic. It hasn’t been easy for the town. But it’s also the reason Marshalltown hasn’t suffered a population and economic death spiral. The town is the same size now as it was then, thanks to the Mexicans and their all-American kids.

What we talk about when we talk about assimilation

In a debate early on in the primaries, Trump criticized Jeb Bush for having spoken Spanish in a town hall meeting. "We have a country where, to assimilate, you have to speak English," Trump said. "We have to have assimilation — to have a country, we have to have assimilation."

Trump is constantly saying what needs to be the case "to have a country," and none of it makes sense unless you interpret him to mean "to maintain traditional American identity." And he has repeatedly defended his call for a blanket ban on Muslim immigration by claiming, falsely, that "there’s no real assimilation" of Muslims to American culture.

But assimilation is a two-way street. The status quo national culture has to assimilate newcomers — that is to say, it has to accept them, welcome them, absorb them — and the newcomers have to assimilate the receiving culture. By speaking Spanish to a native Spanish speaker, Bush was facilitating assimilation by signaling acceptance and inclusion. And that’s a powerful signal indeed, when it comes from the powerful son and brother of American presidents.

From an assimilationist perspective, it’s the right thing to do. Immigrants are most willing to buy into American culture when they sense that it accepts them as fully fledged members of American society. In contrast, Trump’s comments about the non-assimilation of Muslims and Spanish speakers straightforwardly discourage assimilation by withholding inclusion and reinforcing the boundaries between "real" Americans and these immigrant groups.

You can be sure Muslim immigrants and their fully assimilated children and grandchildren heard loud and clear what Trump was really saying — that they couldn’t assimilate because their religion is antithetical to genuine American identity.

The point is that the facts about assimilation are seldom the real issue when assimilation comes up. American culture really is outstanding at assimilating immigrants. Jacob Vigdor, an expert on the measurement of assimilation, finds that "[i]mmigrants are now more assimilated, on average, than at any point since the 1980s."

And this is actually what troubles many white Americans, like Ed Hunter. Assimilation is an issue not because it isn’t happening, but because it is. The issue is that the post-1968 immigrants and their progeny are here at all. And their successful assimilation means that American culture, and American national identity, has already been updated and transformed.

Swift cultural change is extremely disorienting

What we think it means to assimilate depends on what we think American culture is. And what we think American culture is depends on what it was when we were children and young adults.

Human beings are built by evolution to transmit and assimilate culture. But our window for absorbing culture begins to close we as enter adulthood, and the internalization of our culture’s norms and expectations is more or less complete by middle age. (Consider the way we basically stop listening to new music in our early 30s.) Throughout human history, cultural change has been slow enough that that people could expect to pass from cradle to grave within a stable system of social status, moral convention, belief, and symbols of group identity.

Thanks to rapid technological change, economic growth, and increasing global interconnectivity, that’s no longer the case. Swift and dramatic cultural changes can leave us with the baffled feeling that the soil in which we laid down roots has somehow become foreign. Older people who have largely lost the capacity to easily assimilate to a new culture can feel that the rug has been pulled out from under them.

This is something we need to be compassionate about. We have no choice but to rely on our cultural training to guide us through the social world. But when the practical value of the norms and expectations you internalized in your youth begins rapidly to depreciate, it’s almost impossible not to see further cultural change as deterioration — no matter what objective indicators of cultural health may say.

This means that rapid cultural change can make a truly common national identity hard to come by, if not impossible. It’s not clear to me how important it is to have one. But it does seem that a badly bifurcated cultural self-understanding can have very dramatic and potentially dangerous political consequences. David Cameron imperiled the integrity of the entire European Union by fundamentally misunderstanding the facts about the evolution of British national identity and putting it up for a vote. Donald Trump, you may have noticed, has called for a referendum on American national identity, and he’s getting one.

The third stage of grief is negotiation

I try to think about it from the perspective of my Fox News–watching, ex-cop father. The America in which he got married and had children was grappling violently with its primal black-white racial dynamic, but it wasn’t worried about immigration. When I was born, in 1973, the foreign-born population was around 5 percent, close to its lowest point in American history. In 2014, when my son was born, America’s foreign-born population was over 13 percent — its highest point since 1920 — and another 20 percent of the population was the offspring of a parent born abroad.

There is a real sense that we brought our white sons into different countries. By pretty much every measure, it’s a better country — especially if you’re not white, but also if you are. And the version of American identity that prevails among the millennials on the campus of the University of Houston — commercial, striving, patriotic, conservative about family and faith, but multicultural, inclusive, and tolerant — fits the facts of the living, breathing United States of America a lot better than the version that Ed Hunter wants and Donald Trump promises to bring back.

But walls and mass deportation and religious and cultural tests can’t bring anything back. They can only deliver an ugly, fractious, brand new American identity nobody wants.

America’s angry Ed Hunters are telling us they won’t assimilate to the new multicultural dispensation, that they shouldn’t have to. But it’s here, and we need to give them a chance to adapt. Remember, assimilation is a two-way street. Those alarmed by the emergence of an America that doesn’t feel like home need to know that we have every confidence that they are and can be outstanding Americans. They need to know that it is home, and they are welcome here.

Will Wilkinson, a columnist for The Big Idea, is the vice president for policy at the Niskanen Center.

The Big Idea is Vox’s home for smart, scholarly excursions into the most important issues and ideas in politics, science, and culture — often written by outside contributors. If you have an idea for a piece, pitch us at thebigidea@vox.com.