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Last week, Florida Gov. Ron DeSantis refused to allow a cruise ship full of passengers sick with COVID-19 to disembark, on the basis that “we cannot afford to have people who are not even Floridians dumped into South Florida.” He later announced that he would allow 49 Florida residents to disembark from two cruise ships. The more than 250 non-Floridian Americans on board, not to mention the hundreds of others from other countries, are out of luck.

DeSantis’ allegiance to Floridians—only Floridians—is a sign of how the virus is creating an every-state-for-themselves dynamic. It’s not unusual for countries to exempt their citizens from travel restrictions, as the Trump administration has done during the coronavirus outbreak by allowing Americans to return from China and Europe after travel bans were put in place. This is dubious on public health grounds—Americans are just as likely to carry the disease as foreigners—but it makes political sense that governments have a higher degree of obligation to protect their own citizens. It’s more unusual to see this kind of policy enacted at a U.S. state level.

Historian Nick Kapur referred to DeSantis’ decision as “bizarro Floridian nationalism.” This pandemic has already tightened international borders. But as Donald Trump designates certain heavily affected regions of the country as “hot spots,” state residency may start to matter much more than it has in centuries. This virus is likely to leave the United States much less united.

Florida is not going to become an American Abkhazia or Somaliland any time soon. But DeSantis’ stance on the cruise ships was not a one-off. Under fire for spending weeks resisting the kind of social distancing measures that other states have put in place, DeSantis has shifted to scapegoating residents of other states, particularly New Yorkers, for the subsequent rapid growth of coronavirus infections and deaths in Florida. Florida has set up checkpoints along its northern border to screen arrivals from coronavirus hot spots like New York and Louisiana, ordering them to self-quarantine or face jail time. According to the Washington Post, it was a conversation with DeSantis that prompted Trump to briefly consider an enforced quarantine of New York, New Jersey, and Connecticut.

DeSantis is at the forefront of this movement for state border security—ironic for a state as dependent on tourism and northern retirees as Florida—but he’s not alone. Texas has also set up border checkpoints and many have mandatory quarantine policies for out-of-state arrivals. Rhode Island police officers were, for a time, pulling over cars with New York license plates, while the state’s National Guard enforced quarantine orders for arrivals from the Empire State. All this led the Economist to declare that “Federalism, America’s multi-tier political system, is facing its sternest stress test since the Civil War.”

The nature of the virus makes this response inevitable. While no corner of the United States will escape COVID-19 completely unscathed, the trajectories and timing of its spread differ from region to region. And because of America’s polarized political climate and the degree to which the pandemic became a culture war issue in March, different states adopted very different approaches to stop the spread of the disease. States that were lax in adopting social distancing endanger not only their own populations but their neighbors.

Even if they don’t make much difference now that the virus is more or less everywhere, there was some logic, early in the pandemic, of using regional quarantines to halt or at least slow the virus’s spread from one region to another. Back in January, when so many things that are now commonplace still seemed extraordinary, the world marveled at China quarantining Wuhan, a city of 11 million people. This likely helped stop the disease from spreading widely in mainland China outside its epicenter in Hubei province. (There have been only eight reported deaths in Beijing and six in Shanghai, for instance.)

But such measures are, for want of another word, un-American. Even before the coronavirus, Chinese citizens lived with a draconian, if frequently violated, household registration system that prevents them from relocating to another region and makes millions of people effectively undocumented immigrants within their own country. China has “autonomous regions” set aside for ethnic minorities and “special administrative regions”—Hong Kong and Macau—with vastly different political and legal systems.

Despite centuries of arguments over states’ rights, we have no precedent to guide us through the current crisis. The original Articles of Confederation, which envisioned states as far more autonomous political entities than they ended up being, still guaranteed that “people of each State shall free ingress and regress to and from any other State.” The Constitution that replaced the articles doesn’t even bother mentioning the right to travel—it’s basically just assumed in later court cases—but does specify, under Article IV, that “Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.”

These rights have been impinged upon in the past in times of emergency, including in previous disease epidemics, and one would hope that the checkpoints and travel restrictions will be lifted once COVID-19 is contained. But there’s reason to think the effects could be longer-lasting.

Even before the pandemic, Americans were becoming fairly immobile by historical standards. The past few years have seen a small uptick in interstate migration after decades of declines, but the looming recession is likely to curb movement again, just as the 2008 financial crisis did. People are more rooted in their home states, and regional identities are becoming more calcified. America’s political polarization is a regional divide as much as an ideological one.

And it’s not just Republicans who seem to be hoping to carve up the U.S. While American Democrats are traditionally the party favoring a strong federal government, demographic realities and institutions like the Electoral College and the Senate make federal-level politics strongly stacked against them. Liberals may start to rethink the value of autonomous, powerful state governments. Facing congressional gridlock under President Barack Obama and outright hostility under Trump, Democratic states have crafted independent policies on a number of global challenges. Think of California’s ambitious carbon emissions targets or the states that have enacted sanctuary protections for undocumented immigrants. During the coronavirus outbreak, Democratic voters have expressed vastly more faith in state and local authorities than in the federal response.

With the White House telling state governments they’re on their own when it comes to acquiring vital resources, and governors of both parties calling for more interstate travel restrictions, there’s not a whole lot of unity in this crisis.

The cliché is that disasters are when America comes together as a nation. But the peculiar nature of this threat, and the political moment in which it arrived, makes it feel more like it’s coming apart into 50. As we hear frequently these days, the virus doesn’t respect borders—either national or state—and this disunity will only make it harder to meet the next challenge that requires a common response.