The next wave, of more than 18 million migrants, came from southern and eastern Europe and stretched from 1890 into the 1920s. With each wave came an inevitable backlash, as Americans worried that the new arrivals would take their jobs and threaten their way of life. Quotas and restrictive legislation, such as the Chinese Exclusion Act, soon followed.
The 1924 Immigration Act limited immigration so drastically, that it can be discerned by a distinct bend in the chart of US annual population growth.
The most recent immigration wave began in the 1960s, when those restrictions were lifted. Since then, more than 70 million immigrants have entered the US, many from Asia and Latin America, including approximately 18 million from Mexico alone.
In 2024, 14.8% of the US population was foreign-born – an amount equaling the historical peak in 1890, according to the Migration Policy Institute. Immigration accounted for 84% of the total US population growth.
According to Woodard, the early immigration waves - driven mostly by industrialisation - helped boost the political power of the American north.
And that geographical imbalance helped further fuel ideologically divides.
Southern leaders pushed for territorial expansion – and an expansion of slave states – to ensure they maintained political power at the national level, before they broke off altogether, starting the Civil War.
But modern trends have reversed this geographical divide. Many immigrants - and northern transplants - are now drawn to the south, especially the bustling economies of cities in Texas and Florida. While a recent wave of illegal immigrants at the southern US border has heightened tensions.
Trump's populist conservatism, then, can be seen as a response to America's shifting centres of power.
Upon returning to the White House, Trump has delivered on his campaign promise to pursue mass deportations.
Meanwhile, he has expressed a nostalgia for the territorial expansion of the 19th Century, with talk of acquiring Greenland, repatriating the Panama Canal and adding Canada and Venezuela as "51st states".
His version of American expansionism is thus a kind of mirror image of last 250 years of history. The country spent its first century expanding physically, then stopped trying to get new territory and focused - sometimes haltingly - on opening the nation to immigrants.
Now, Trump has changed course, with aims to expand America's physical borders again, and limit the number of people the country lets in.
Trump and his supporters say that the character of the American nation is in danger of being fundamentally and permanently changed. "We won't have a country anymore," is a common Trump refrain about the dangers of mass immigration.
"That does not come out of nowhere," said Woodard. "We have the meta struggle in American history: Are we a civic nation devoted to ... a society where every individual human can be equally, universally and sustainably free over time? Or is this a state that belongs to a certain group of people that are the real Americans by blood and descent?"
In the vast stretch of world history, 250 years is a blip, a flash, a blink of the eye. But for the US, 250 years has been transformational – even if the divisions at the heart of the nation, and the concerns about its future, have been an enduring feature.