The US government’s immigration policies are rooted in a refusal to accept demographic change and loss of power

Last week immigration and border security issues roiled US politics more than ever. No one doubts the intensity of the argument, but few realise that the very future of American democracy may be at stake.

Everyone agrees that there is a crisis on the southern US border, with an extraordinary number of people seeking asylum for humanitarian reasons.

However, Americans have no common narrative.

Therein may lie the outcome of the 2020 presidential election. That is certainly Donald Trump’s calculation.

Mr Trump successfully sought the Republican nomination, and then the presidency, by claiming that there was an immigration crisis involving an invasion of Mexican rapists, criminals and gang members.

It was entirely fictional and cynical.

However, partly because of his own policies, a genuine border crisis has now developed.

Ostensibly, this is about a clash of American values.

Republicans claim to be protecting US laws and territorial integrity. Their rhetoric effectively no longer recognises that asylum seekers exist at all – all undocumented border-crossers are assumed to be economic and illegal migrants.

Although the appalling treatment of migrant children by the authorities is part of a harsh strategy of deterrence, the infrastructure is overwhelmed by an unexpected flow of people from El Salvador, Guatemala and Honduras.

Some Democrats are so horrified by the outrageous conditions under which these families, and children, are held at the border that they oppose any additional funds for these agencies.

The Democratic Party was badly split last week between a majority that wanted to provide funding, with clear basic treatment conditions, to care for these people, and a left-wing minority that wanted to deny all funding to support what they see as the unjustifiable detention of families and children, especially without clearly stipulated minimal care conditions.

Funding was ultimately approved by Congress when Vice President Mike Pence privately assured House Speaker Nancy Pelosi that the Trump administration would abide by many of the proposed care conditions that were dropped from the funding bill.

The immigration controversy, however, is a symptom, and a subset of the far larger issue of the increasing demographic and cultural transformation of the United States, away from a white, Christian majority to a far more diverse society that no longer resembles the traditional, normative American ethnic and cultural self-perception.

This is a traumatic moment for many white Americans, and echoes other dangerous and disruptive transitions in US history.

Mr Trump accurately believes he was elected primarily on the basis of a racial and ethnic appeal. He is determined to run for re-election on the same implicit ethnonationalist platform.

He has therefore purged the immigration services of relatively moderate managers and installed hyper-aggressive administrators with absolutist views on immigration and asylum similar to his own.

On Twitter, he darkly warns of a national sweep to deport thousands, if not millions, of undocumented families.

Beneath all this lies the fundamental question of whether much of the non-urban white, Christian American population is prepared to accept calmly that it will soon no longer be the majority US community, and that the country is on an inexorable path towards being far more diverse and cosmopolitan than in the past.

Urban white, Christian populations appear ready to accept this, but many non-urban ones may not be.

This is, therefore, a historic and extremely dangerous turning point in American history.

It has at least two clear precedents, in which hyper-empowered constituencies have sought an alternative to fully realised democracy when its outcomes did not suit them.

The Civil War was the result of the refusal of an enraged, slave-owning minority of once-dominant southern states to accept the election of Abraham Lincoln. It riled them so much that they eventually tried to undo his election by seceding from the United States, despite no provision for that in the Constitution.

During the 1930s, indignant sections of the middle and working classes, having been atrociously impoverished by the Great Depression, seemed on the brink of overthrowing both democracy and capitalism. Only the radical reformist New Deal of Franklin Delano Roosevelt, and the subsequent massive stimulus of the Second World War, salvaged American capitalism and democracy from potential revolutionary overthrow.

How large the constituency for revolutionary socialism might have become as the Great Depression dragged on is not knowable, though it was clearly huge. What is vital is that, again, a significant section of the US public was apparently prepared to place specific, urgent interests over the democratic political system.

As with the Civil War, they were ultimately brought to heel. But in both cases, it was a close call.

The United States seems to be again entering a historically transformative period, in which a large section of the population will have to ask itself whether it prefers the basic structures of democracy over its own narrow, communal and sectarian interests.

That’s what the immigration debate – and arguments about partisan gerrymandering, a citizenship question in the census, and many other current controversies – are really about.

Are non-urban white, Christian Americans willing to accept a significant degree of narrow, communal disempowerment to preserve democratic processes and values? Or, are they prepared to jettison democracy, in whole or part, if it threatens their identitarian interests?

That, at its core, is the question now facing the United States.