There is nothing an American politician likes more than talking about leadership.

When one among them achieves the presidency, the job of leading others is assumed, and assumed to be global. The US leads; all those of decent intent must follow.

Whether the world wishes to be led is a topic too often neglected. Doubt sits badly with American exceptionalism: who wouldn’t buy the dream? But there is another, harder question for a nation fond of its self-image as the home of democratic virtue.

What happens when the US itself becomes ungovernable, and incapable of being led? What happens if, when it comes to leadership, domestic and global, America sucks?

The last few days and weeks have provided evidence for the prosecution. We have seen a president apparently determined to turn disappointed hopes into a career motif. We have seen a conservative cabal engaged in political hostage-taking for the sake of a strange, ecstatic nihilism. And we have seen the global economy taken to the brink of chaos because people in Washington think little and care less about “the world”.

It’s epochal, after a fashion: very soon, the “leadership” offered by a country with a $14.3 trillion debt and a dysfunctional political system is liable to be discounted, despite all those nukes. The Chinese, holders of most of those trillions, are already exasperated. Europeans, still paying for America’s failed banks, are aghast. And why not? US democracy, that 20th-century exemplar, has become irrational.

A simple, technical accounting manoeuvre – the raising of the debt ceiling – has been transformed into political warfare. The Tea Party, its sub-sects and its Republican prisoners, has risked an American default and a planetary depression just to prevent the re-election of Barack Obama. Acquiring a plausible candidate might have been a better move: they lack that luxury.

They pretend – it’s quite a trick – that the black guy invented “debt”. They forget that George Bush, like Ronald Reagan, raised the ceiling repeatedly while piling up IOUs as if – for you never knew – there was no tomorrow. Bill Clinton was the last president to attempt to balance America’s finances. Mr Obama, what with legacy banks and legacy wars, stood no chance.

He also took the quaint view that the US might reorder its affairs without pillaging the minimal dole granted to the poor, the sick and the vulnerable. He thought the better-than-rich might surrender the tax cuts for which Mr Bush accumulated still more debt. Mr Obama did not grasp – still does not grasp – what was involved in the Tea Party challenge.

They invoke the founding of the country. Or rather, they invoke the myth – sometimes Jeffersonian, more commonly from Aaron Burr – of sturdy, well-armed, God-fearing folk who hold banks, government and taxes alike to be iniquitous, who believe in national defence and not much else (least of all gay marriage). Fundamentally, the Tea Party is grounded in the belief that Mr Obama has no right to be president: he’s not “their America”.

It’s an interesting concept of democracy, far less of patriotism. And yet, as the comics ask, what just happened? Democrats have the presidency and the Senate, two legs of the tripod. They have sufficient numbers in the House of Representatives, even yet, to prevent a debt ceiling deal that hammers the poor while adding no tax burden on the rich worth the name. But their leader caved: Mr Obama surrendered.

Some of the chatter from the Beltway says this was very smart. The President, supposedly, was doing the clever thing and allowing the country to decide just who had brought the world’s largest economy to the verge of humiliation, default, and the loss of its AAA credit rating. Mr Clinton pulled the same trick, says the chat, in 1995, and was re-elected.

The US economy was in vastly better shape then. Mr Clinton could trim and triangulate with the best of them, but he won the rhetorical war with Newt Gingrich and his tribe. Mr Obama seems intent only on getting the debt ceiling problem out of his in-tray before he commences his re-election efforts.

It may not be smart, but it doesn’t count as entirely stupid. On this side of the ocean we are too easily impressed by the rhetorical extravagances of the Tea Party’s stentorian Munchkins. Mr Obama understands America better. The old and white people who adore Sarah Palin are diminishing in number, year on year. Those who are black, Hispanic or young decide elections now. And Tea Party debt mania does them no good.

That doesn’t help America, or the world. Mr Obama has decided, it appears, that being weak is a strategy. He calculates in terms of electoral advantage rather than the national interest. He has the debt ceiling he wanted, more or less, and probably believes he can fudge the cuts in 2013 and beyond. But he has surrendered his beliefs.

He allowed the Tea Party, yet again, to dictate the terms of engagement in American political life. He allowed his country – and the rest of the planet – to believe that minority obsessions were of overwhelming importance. By no coincidence, he didn’t deal with the fundamental issue of debt. Instead, he read the House voting numbers.

It’s not much of a basis for “leadership”, whatever the excuses. Mr Clinton was cunning; FDR was vulpine in negotiations. John Kennedy betrayed true believers time and again, without a second thought. There comes a point when you have chalked up all the brave battles and lost the damned war. Will the youth of America turn out again for Mr Obama and “change” next year? I doubt it.

The democratic model offered to the world seems a little tattered this morning. In essence, the US will allow itself to borrow a few hundred more billions, screw the poor, and accept that its entire system can be held to ransom by – as Dr Vince Cable would say – “right-wing nutters”. As for “the world”? No-one on the Hill was much interested.

I think we had better call that a lesson, if wise, and arrange our affairs accordingly.

l Foreign news: page 14