The cold war film Dr Strangelove owes its shelf-life to its portrait of US-UK, not US-Soviet, relations. The straight man of the piece is a British exchange officer who must talk American hot-heads out of a nuclear first-strike. There was more to this account of the US as a feral giant than the snark of an Anglophile director. Real life bore it out when Britain abstained from the Vietnam war. It continued to chime as London tried to nag Washington into such internationalist ventures as the Kyoto protocol and the Iran nuclear pact.

How weird to be living through a reversal of these roles. For perhaps the first time since the Suez crisis, the US is the more committed of the two nations to the norms and institutions of the global commons. As Britain tampers with the Northern Ireland protocol, an Irish-American president looks on with scarcely concealed dismay. While Joe Biden aims to increase US foreign aid, Britain, according to one of its own government’s MPs, is the only G7 state to make a cut.

And this comes after an odd few years for Britain’s moral standing in Washington. There was no shame in the initial cultivation of President Donald Trump. Emmanuel Macron made no less a fuss of him during his first summer in charge of France.

What distinguished (if that is the word) Britain was the decision to keep it up after it became plain that Trump was bent on a spoiling role in the world. The governing Democrats are too busy to be vindictive about such bygones. But the German chancellor, Angela Merkel, who kept a scrupulous distance from the last White House, will be the first European leader to visit the new one.

It is hard to convey the desire in an Asia-facing US for zero distractions in the rest of the world. The waiving of sanctions over the Nord Stream 2 pipeline, the exit from Afghanistan, the presidential talks with Vladimir Putin, all suggest a nation set on minimising non-Chinese sources of stress.

To that end, Biden views the EU (a “strong and vibrant entity”) as a guarantor of European cohesion, like all pre-Trump presidents. In Washington, there is no bitterness or even much discussion any more of Britain’s decision to leave it. But nor is there the slightest qualm about engaging with the continent through Berlin or Paris, if London renders itself peripheral or eccentric.

The logic of Brexit might further distance the two countries. To make a go of it, the UK will have to show an opportunism that jars with Washington’s new view of the world. One case in point is regulatory and tax competition. The ink was still damp on the US-led accord for a minimum corporate tax rate when Britain suggested exemptions for financial services.

On a grander canvas, a post-EU UK must also entertain Chinese trade and investment, with all the qualms that implies in Washington. It is true enough that several G7 members favoured a softer communiqué on China than Biden secured over the weekend. But only one has just lost the safety in numbers of its regional trade bloc.

For all the pomp of the new “Atlantic Charter”, Britain and America will keep returning to this crux. The point of Brexit is the flexibility to scour the world for commercial and diplomatic openings. But the new US vision is one of pan-western solidarity: against economic undercutting, against the raw weight of China.

It is a vision that animates Biden ever more. With his domestic plans stalled, his best chance of a consequential presidency lies abroad. In essence, he is going through a sped-up version of the outward turn that US leaders perform after a midterm loss of Congress.

For a sense of the change, consider that it took him only a reported two hours to call Israel’s new prime minister, Naftali Bennett. His predecessor, Benjamin Netanyahu, waited almost a month for the same contact. Whether this reflects anti-Netanyahu pique or a less pandemic-occupied Biden, it amounts to the same thing: a president who regards shoring up the west as an ever larger priority.

All UK governments get things wrong about the US. My favourite is their inflated sense of how many Americans have an ancestral link to Britain (even the white ones are more likely to be Germans than “cousins”). But this one stands at a particularly odd angle to the White House.

You have to be in at least the September of your life to remember when it was the US chiding the UK to honour global norms. If those days are back, the junior nation should not assume it will be costless.