That was partly the message from Michigan last week, where younger voters used the Democratic presidential primary to signal dismay over Biden’s unstinting backing for Israel’s war with Hamas. For sure, he has gradually become more critical of Benjamin Netanyahu’s criminal clique – and is finally pushing a ceasefire. But his lethal, almost callous misjudgments following 7 October will not be forgotten.

Biden is not the admired foreign policy maestro he seems to think he is. Hundreds of US officials have publicly rejected his Israel policy. So have European and Arab allies, amazed he’s so out of touch.

In a pompous “urgent message” to Biden last week, the New York Times columnist Thomas Friedman warned, belatedly, that America’s global standing was plummeting alongside Israel’s.

“I don’t think Israelis or the Biden administration fully appreciate the rage that is bubbling up around the world ... over the deaths of so many thousands of Palestinian civilians, particularly children, with US-supplied weapons in Gaza,” Friedman wrote. This is hardly a fresh insight. Biden, deaf to – or careless of – fury overseas, clings to outdated thinking based on Israeli exceptionalism and entitlement. Sometimes the Atlantic seems very wide indeed.

Biden may be finally waking up to his Israel-related electoral peril. The 13% of Michigan Democrats who voted “uncommitted”, rather than for him, could spark a rolling, nationwide de facto boycott of his candidacy, starting with this week’s Super Tuesday primaries. Biden will surely win his party’s nomination. But his cause is tarnished.

Polls suggest that Americans are more concerned than usual about the state of the world – and this will influence how they vote this autumn. On Gaza, Biden has lost majority support, according to a recent survey. Only 31% of US adults approve his handling of the conflict. Half of all Americans believe Israel’s military has “gone too far”. Ominously, among voters aged 18-29 who backed him en masse in 2020, Biden now trails Donald Trump.

Another poll found that while 43% of Americans believe Biden responded well to the Ukraine invasion, 58% now back a negotiated settlement. Biden’s view that the war symbolises a worldwide struggle to defend democracy is not widely shared. Most voters say the primary US aim should be to prevent escalation and further suffering.

Support for Ukraine among Republicans is weaker than among Democrats.

That’s one factor driving Trump’s apparently unstoppable, parallel drive for the Republican presidential nomination – underscored by his trouncing of sole rival Nikki Haley in Michigan – and the blocking by his supporters in Congress of Biden’s latest Ukraine aid package. Trump says what he dislikes, loud and often, but struggles to articulate solutions.

Trump’s hyper-nationalistic, prejudice-filled, fact-free America First platform reflects deep hostility and ignorance of the world and a visceral desire to disengage.

This manifests itself in sneering contempt for Nato, the EU, most Europeans, all migrants, free trade, environmentalists, the UN and international treaties; indulgence of autocrats and like-minded anti-democrats such as Putin; and an overly aggressive attitude to competitors such as China.

Despite some convergences, the choice between Trump and Biden on foreign policy and America’s international role is stark. Trump wants to be world top dog, yet rejects the responsibilities of global leadership. Biden, a firm believer in the US as an indispensable nation, enthusiastically embraces them. Worryingly, public opinion may be tipping Trump’s way.

The annual Gallup world affairs survey, conducted last month, found fewer Republicans than ever (61%) think the US should play a leading or major international role. The Biden-era idea of the US as global policeman is now supported by only 65% of Americans overall. Around 10% of Republican voters favour complete isolation.

These findings only serve to reinforce the view, taking root among European and Asian allies, that US global leadership, dominant since 1945, is experiencing epoch-ending, terminal failure – that the Pax Americana crumbles. What they see is two elderly men locked in an ever more destructive, inward-looking electoral knife fight.

One, well-meaning but weak, is a hostage to times past, when the ubiquitous US superpower led as a matter of course. That time is over. He doesn’t get it.

The other represents the very worst of America – selfish, exploitative, uninformed, insular, illiberal, self-obsessed and vicious. Little wonder Europe’s leaders are in a tizzy, clinging to each other like panicky passengers in a sinking lifeboat, arguing about what to do. What shocks to the global order are now in prospect!

This warped and ugly “other America” is no trusted friend, no ally, no partner for the democratic world. Shining city upon a hill no more, it’s an enemy in the making.