Wake up, Britain: Donald Trump’s US is no friend of ours. We must secure our own place in the world | Simon Jenkins

If Americans vote for a Republican majority in both houses of Congress in November, “I will issue a dividend to every adult citizen in the United States of America for $5,000.” But they must not spend it in Canada or China or anywhere else outside the US. So said Donald Trump in Texas on Wednesday in advance of the forthcoming midterm elections. He further told voters to “Pretend that I’m on the ballot”. It was a climactic moment in an almost two-hour rant.

Trump does not have the required trillion dollars in his pocket, and it would be illegal to disperse such a sum without congressional approval. In any case, JD Vance now appears to have rowed back on the promise.

Observers from abroad must beware: it is unwise to subject Trump’s populism to the discipline of truth. Trump also said Americans should thank him for attacking Iran since that country was “two, maybe three weeks away from having a nuclear weapon”, which it intended to use against them. It was the old Saddam Hussein gambit.

The problem is that almost every one of Trump’s speeches refers back to himself, as if he and the United States were synonymous. He claimed to have won the presidency three times. He says: “If we hadn’t won the last election, I’m not sure that our country right now would even exist.” He added that the arena where he was speaking was packed, with crowds outside clamouring to get in. Pictures show it half empty.

Anyone watching can see why there has been much medical debate over whether Trump is exhibiting signs of narcissism disorder. Key symptoms are mendacity and inconsistency. In 2021 members of the House of Representatives called for the constitution’s 25th amendment, by which a president can be declared unfit for office, to be invoked over the Capitol Hill riot. But that has a high constitutional threshold, requiring a majority of his sycophantic cabinet to declare him unfit.

As for more conventional checks on a wayward president, they have proved extraordinarily weak. A Congress over which Trump exerts a populist terrorism has been reluctant to use its powers to call him to account. He has flagrantly declared wars without congressional authority, abused executive orders as “emergencies” and frozen federal spending to halt the “advance [of] Marxist equity”. He has even tried to redefine US citizenship, which is unconstitutional.

Very gradually some institutions supposed to hold the White House in check are finding muscle. Judges have blocked attempts to limit birthright citizenship. Trump’s blanket firing of public officials is being legally challenged, although the supreme court has often sided with him. Even the Senate Republican leader, John Thune, has balked at Trump’s proposed Save America Act – which would require anyone voting to show documentary proof of US citizenship. Its outrageous gerrymandering would shrink Democrat votes and aid Republicans. It is an echo of the Jim Crow laws of the post-civil war south.

Where this president leaves the US’s longstanding allies overseas is less clear. Visitors to the British embassy in Washington are traditionally warned that “we disagree with America about almost everything, but remain the closest of friends”. Britain distanced itself from war in Vietnam but joined the US, inexplicably, in Iraq. But nothing has come near Trump’s sustained abuse of Britain in the past year on everything from defence spending to wind turbines. He sees the UK as “weak” and “on the edge of disaster”. It was “once” the US’s greatest ally. But by implication, is no more.

This opens the central weakness in Anglo-American relations that Trump has made explicit. This is the assumption that the US would honour the principle of collective defence and go to war with Russia, in the event that Russia declared war on Europe. This held during the cold war, with the US’s guarantee of Europe’s security taken as axiomatic.

Since the end of the cold war, that guarantee has become ever more flimsy. Despite events in Ukraine, it has long seemed implausible that Russia would declare nuclear war on the west, let alone on America itself. It is therefore equally implausible that the US could threaten Russia with nuclear retaliation.

At which point a central essence of the Nato alliance starts to crumble. European governments have seen a president ready to annex foreign countries, invade others, disrupt world trade with aggressive tariffs and defy international law. Can such a wayward and egocentric man, devoid of domestic constraints, really be relied on to exercise extreme caution and dependability in circumstances where nuclear weapons are at issue – whether or not the end of the cold war has diminished the threat of east-west confrontation?

In other words, nations should start looking realistically at the defence of their own continent and their own borders. There is no new world order any longer. That balloon has been punctured.

Friends of the US have always relied on its constitution to hold autocratic presidents to the straight and narrow. But not since Andrew Jackson in the 1830s has there been one who flouts law and convention as brazenly as Trump. Over the next two years his nation’s political institutions are to be sorely tested. But then he will be gone. Perhaps only then will Britain learn his legacy.

• Simon Jenkins is a Guardian columnist