Here’s one reason Donald Trump seems perennially in a bad mood: he has probably figured out that the America he fantasizes about is out of his reach.

However many immigrants he manages to deport or prevent from entering the country, the white paradise he is promising his Maga base, free of Somalis, Mexican “rapists” and generally people from “shithole countries” – closer in hue to the America where he was born – is not his to offer.

He can, however, do a lot of damage. By doing his best to make the US unbearable both to foreigners and, more generally, people from ethnicities that do not mesh with his picture of the American family, Trump is not Making America Great Again. He is ensuring America will be smaller, older, weaker and easier to push around.

Even zeroing-out immigration altogether will be insufficient to restore the bygone America that Trump yearns for. Whatever he does to get rid of immigrants will not stop the non-Hispanic white footprint from shrinking.

Trump is not the first politician to try to protect their conviction about the whiteness of America’s racial stock from “foreign” contamination. The national-origin immigration quotas in the Johnson-Reed Act of 1924 were quite successful at doing this. In 1960, 75% of immigrants to the US came from Europe.

But the levee broke. The Hart-Celler Act of 1965 replaced national-origin with family ties. These days only about 10% of immigrants hail from Europe. More than half come from Latin America. When Trump was four, white people accounted for nine in 10 Americans (the census did not ask about Hispanic ethnicity). By 2024, the non-Hispanic white share had slid to 57.5%.

Nothing Trump does to stop immigration can change this trajectory. Because the non-Hispanic white population will keep on shrinking regardless, the Census Bureau projects that it will lose 3.6 million people over the next five years, almost 11 million in the decade after that and more than 14 million in the subsequent one.

And that means that if Trump and his ethnonationalist sidekick Stephen Miller achieve their goal of cutting future immigration down to nothing, the US population will shrink pretty sharply. It will be 6% smaller by mid-century, 10% smaller by 2060 and one-third smaller in 2100. The president may not fully realize this – his grasp of economics has proven tenuous – the demographic squeeze would come at a substantial cost.

The population will not merely shrink. It will get old, because the population of working age will shrink even faster. Today, people over 65 account for about one-fifth of the population. In a zero-immigration scenario, their share will rise to one-quarter by mid-century and over one-third by its end, supported by a shrinking labor force.

The data does preoccupy people in the White House. Their prescription, however, is as unrealistic as the rest of their dreams: to boost American fertility, which has been falling over the last two decades and is now at 1.6 children per woman of reproductive age, substantially below the roughly 2.1 replacement rate needed to stabilize the population.

Part of the problem is that declining fertility is a global phenomenon that scholars do not fully understand. It is happening not only in rich and middle-income countries but also in the world’s poorest countries, where fertility remains comparatively high. Pronatalist policies in developed nations, including child benefits, broader provision of childcare and other family supports, have had a limited impact on families’ propensity to have kids.

The other problem is that the proposed solutions from the Trump administration border on the absurd. They include a “National Medal of Motherhood” for particularly fecund mothers, fertility tracking classes and $1,000 to be deposited into “Trump accounts” for babies born during his presidency. These come amid a torrent of policies that will make childbearing tougher, such as cuts to federal support for children’s healthcare and nutrition, courtesy of the president’s tax-cutting bill.

Trump’s problem, in a nutshell, is that the one straightforward policy approach to ease America’s demographic challenge is to rely on people for whom he has expressed unconstrained disgust: non-white immigrants.

In the Census Bureau’s high immigration scenario – in which net immigration averages some 1.5m per year – the US population would grow 13% by 2050 and 28% by the end of the century. The 65-plus share would not hit one quarter until 2070.

One challenge to this scenario is that there may not be sufficient immigrants available to keep propping up the American population, especially as fertility rates drop in Latin America and Asia too. Net immigration to the US averaged 1.8m per year between 2020 and 2024, driven by a surge after the Covid pandemic. But it only hit about 900,000 a year in the decade before that.

The bigger conundrum for the president is another, though. The unadulterated, non-Hispanic white footprint will shrink under any scenario. But if immigration is high, it will drop faster: from 58% of the population this year to under 47% in 2050. The Hispanic share would rise from just under 20% to almost 26%.

The challenge must be torturing the guy: if Trump wants to keep America great, he must let it get browner.