So what would the decline of America look like? I don’t ask the question because I think it’s happening (yet?), but because even the most inveterate optimist should be interested in the dangers, if only to ward them off.

Here’s the cleanest tale of hypothetical decline I could come up with, keeping away from the more partisan or hysterical scenarios, or those involving a catastrophic deus ex machina.

Imagine that the United States gets through the presidency of Donald Trump without a crippling constitutional crisis. Still, the shrill public debate — which will continue well past Trump’s time in office — will continue to prove unequal to the task of addressing the nation’s most pressing problems.

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In recent years, the underlying rate of productivity growth often has been about 1 percent, and rates of economic growth are not even half of what they used to be. Meanwhile, America will have to increase taxes or reduce spending by about $2,200 per taxpayer per year to keep the national debt-to-GDP ratio from rising ever higher, and that figure predates the Trump tax cuts. To fund that shortfall, the U.S. will cut back on infrastructure maintenance. At least one-third of this country will end up looking like - forgive the colloquial phrase - “a dump.” The racial wealth gap will not be narrowed.

Aging and entitlements will force the president, whether Democratic or Republican, to look for a mix of spending cuts and tax increases. The spending cuts will diminish the range of the military, and the tax hikes will ensure that economic growth doesn’t pick up. The integrity of Medicare and Social Security will be (mostly) protected, but the U.S. will lose the ability to project power around the globe.

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Over a period of less than five years, China will retake Taiwan and also bring much of East and Southeast Asia into a much tighter sphere of influence. Turkey and Saudi Arabia will build nuclear weapons and become dominant players in their regions. Russia will continue to nibble at the borders of neighboring states, including Latvia and Estonia, and NATO will lose its credibility, except for a few bilateral relationships, such as with the U.K. Parts of Eastern Europe will return to fascism. NAFTA will exist on paper, but it will be under perpetual renegotiation and hemispheric relations will fray.

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One area of major technological advance will be drugs, and I don’t mean beneficial pharmaceuticals. The opioid crisis eventually will subside, but new waves of ever more powerful addictive substances will arise. Easy home lab production will make interdiction at the border fruitless. More than 80,000 Americans already die from alcohol every year, and more than 60,000 from drug overdoses. Total losses from addiction will rise.

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Other technologies will indeed provide a bounty, but not all of it will be positive. Artificial intelligence and facial and gait surveillance will lead to unprecedented invasions of privacy, causing another 1 or 2 percent of Americans to decide to “live off the grid.” The impact of assassin drones will be curbed - by filling the skies with police drones. Public crimes will plummet, but public spaces in major cities will have a depressing sameness, due to the near-total absence of spontaneous behavior. Advances in recording technologies will make most conversations in public, and many in private, remarkably bland.

Driverless cars will be “the next big thing,” but they’ll make roads more crowded. The elderly will insist on their driverless car rights, and defeat economists’ proposals for new congestion charges. Americans will spend another hour a day in their cars, although texting and watching TV, rather than driving.

The very worst fears about climate change won’t come true. But a nagging succession of storms, plus required adjustments along the coasts to accommodate a rise in sea level, will eat up about 0.5 percent worth of economic growth. So when America does occasionally approach 3 percent growth, in terms of living standards it may feel more like 2 percent.

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Shall I present my own petty gripes? Due to the limited selection on Netflix streaming, fewer and fewer people will watch the great movies of the past, thereby neutering the durability of the 20th century’s greatest art form. And live performances of classical music - another of the West’s most significant and beautiful achievements - will cease to be regular in all but a few major U.S. cities.

So what in this description sounds so implausible? Is it that you think productivity growth will come in at 3 percent? That it will all be worth it because advances in medicine will allow us to stick around in decent form until age 135? That technological breakthroughs will extend the reach of the U.S. military further yet? That the Mars colony will be awesome?

Just how lucky are you feeling?

Cowen is a Bloomberg Opinion columnist. He is a professor of economics at George Mason University and writes for the blog Marginal Revolution. His books include “The Complacent Class: The Self-Defeating Quest for the American Dream.”