Even more than his first victory in 2016, Donald Trump’s re-election marks a historic disruption. It is a profound moment of change, not just for the United States but for the rest of the world, too. For decades, the US has been the free world’s essential and reliable nation. Not any more. It could even one day become them against us.

Trump 2.0 seems certain to put one of the final nails in the coffin of the post-1945 Pax Americana. In reality, that old normality has been disintegrating since at least the Vietnam conflict. George W Bush’s “war on terror” caused more problems than it solved. Barack Obama and Joe Biden were each reluctant to wield America’s big stick, most recently and tragically in the Middle East. Now, though, there is no hiding from the realities.

Under Trump, the global agenda will alter, whether we like it or not. The battle against climate breakdown will take a gut punch, international relations will become more transactional, Ukraine’s fight against Russian aggression may be stabbed in the back, and Taiwan will be staring down the barrel of a Chinese gun. Liberal democracies everywhere, Britain included, will also come under fresh siege from their own Trump imitators, powered by truth-spurning social media.

American voters have done a terrible and unforgivable thing this week. We should not flinch from saying they have turned away from the shared ethos and rules that have shaped the world, generally for the better, since 1945. Americans have concluded that Trump is not “weird”, as it was briefly fashionable to claim, but mainstream. Voters went out on Tuesday and voted weird in huge numbers. Americans must live with the consequences of that.

Other democracies, including Britain, need to understand what is at stake. The challenges facing the international order are only the start of it. Challenges on the home front are just as real. Democracies need to respond, far more soberly and determinedly than many have yet done, to the digital-era power of Trump’s nationalist, protectionist and resentment-fuelled messages. If we want to avoid being overwhelmed by similar forces, leaving us even more vulnerable to hostile autocracies such as Russia, we need to be proactive, not passive, about them. Without that, we may find ourselves governed from Clacton-a-Lago.

The ultimate foolish response to Trump’s election from democracies would be to shut our eyes and ears, and repeat our liberal pieties even louder than before. Trump’s re-election is a shocking event, but the shock ought to force the democracies into much more serious action against the widening economic inequality and the fear of migration that drove this week’s result.

For Britain, which has clung for so long to illusion and to lazy imitation of the US, this is a moment of particularly difficult choices at all levels. Keir Starmer, his popularity already slipping, will nevertheless lose more than he gains by acting, as he did in the Commons today, as though Trump offers continuity. The Liberal Democrat leader, Ed Davey, was right to challenge him over Ukraine and a possible trade war. Starmer needs to face these facts, not duck them.

But there is something far larger involved for Britain. This country clings to the belief that it enjoys a special relationship with the US. Above all, this rests on the belief in a commonality of values, economic interdependence and a certain cultural shared space. The relationship is widely deemed to benefit Britain in hard and soft ways.

Yet where, after 5 November 2024, is the commonality? What do our largely secular societies truly have in common with a nation whose religiosity drives it to outlaw women’s reproductive rights and, in some cases, to see Trump as a leader sent by God to save the US from socialism? Our culture is not theirs, nor theirs ours. With Trump’s re-election, claims to commonality are dangerous self-delusion. We need to lose those infatuated stars from our eyes.

The reality is that we are, as Oscar Wilde said, two peoples divided by a common language. Americans have just done their best to prove this. Polling in this country underscores the point from the other side. Only 21% of British adults thought Trump’s victory would be “a good thing”, according to one recent poll. Another found that 61% backed Kamala Harris against 16% for Trump. And remember, Britain is very much in line with other European countries on all this.

Since Trump’s re-election threatens most Europeans, perhaps Britain should move closer to Europe? It is a legitimate question, and not to be dismissed merely because Brexit makes it difficult, though it does. Undoubtedly, Britain’s principal foreign policy relationship will now lie in Europe once more, not elsewhere. But there is no point reopening all the wounds of Brexit. The Labour government’s pragmatic reset with Europe on defence, trade and security remains a more practical approach.

There is one small possible consolation from Trump’s lamentable re-election: the event is so shocking that it may finally help to nudge the British into seeing Americans as different and ourselves as we really are, no longer reliant on the crutch of the supposed special relationship. All waning imperial powers struggle with their own inheritances, as 19th-century powers such as Britain, France and even Russia are all doing in different ways. The US, a much later imperial power, has barely begun the process.

Above all, Trump embodies the seductive deceit that imperial decline can be reversed and lost self-assurance restored. Parts of white Britain are not immune from a similar longing at times. Yet Britain as a whole, in its heart of hearts, is on a complex journey away from the overbearing past. With the failure of Brexit, and now faced with the Trump re-election too, the country has little alternative.

• Martin Kettle is a Guardian columnist

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