©Matt Kenyon

The magical thing about America’s federal system is that when the centre stalls, the rest keeps calm and carries on. The US economic recovery is happening despite engine failure in Washington. This is just as well since there are few engineers to hand. No such fail-safe device exists for foreign policy. It used to be said that US politics stopped at the water’s edge. But the atrophy is seeping into every corner of US global engagement — from Israeli relations to Pacific trade talks. The costs are largely invisible. Yet there is a real price for the country’s growing unpredictability on the world stage.

Things were meant to be taking a turn for the better by now. When Republicans took control of Congress in November a line was supposedly drawn under the previous six years’ impasse. Until then, they could block everything the president wanted safe in the knowledge that inattentive voters would blame the Democrats. Once Republicans had control of both chambers, voters would hold them to account. That forecast already looks too rosy. The Republicans are as opposed to Barack Obama’s domestic agenda as before and the Democrats are in disarray. Instead of breaking the logjam, gridlock is spreading like an inkblot into US foreign policy.

Capitol Hill’s disunity is also hindering Mr Obama’s ability to wage war on the Islamic State of Iraq and the Levant, also known as Isis. Part of it is self-inflicted. By declaring that he will not put US boots on the ground, Mr Obama has limited the Pentagon’s ability to advise the Iraqi army on the battlefield — much to Baghdad’s annoyance. Iraqis partly blame Mr Obama for their failure so far to recapture Tikrit. But Capitol Hill is making the problem worse. Mr Obama has requested authorisation to fight Isis. Republicans believe he is asking for too little authority and Democrats believe he is asking for too much. The upshot is that Mr Obama is unlikely to receive approval from Congress, which will further cramp his political leeway to wage war on Isis. Until recently, the fight against Islamist terrorism was mostly bipartisan. It, too, is now gridlocked.

The threat to Mr Obama’s trade agenda is also growing. To wrap up the 12-member Pacific trade talks, he needs fast-track negotiating authority from the US Congress. Each of his predecessors has received it. Here was one area — free trade — where a Republican majority could work in the White House’s favour. Alas, more wishful thinking. The left remains implacably opposed to any trade agreement — the AFL-CIO, America’s largest union, has promised to stop funding any Democrat who votes for the Pacific deal. Meanwhile, Tea Party Republicans are loath to grant Mr Obama plenipotentiary negotiating powers. Their support for free trade is eclipsed by their dislike of Mr Obama. With each week, his trade ambitions look a little more wobbly.

Gridlock is even undercutting Mr Obama’s “pivot to Asia”. Observers blame him for the fact that US allies, led by Britain, are rushing to join China’s Asian Infrastructure Investment Bank against America’s wishes. Mr Obama has failed to spell out the conditions under which the US would lift its opposition. But the problem originates on Capitol Hill. China’s desire to create a parallel set of multilateral institutions stems from the US’s inability to reform existing ones. US Congress stands alone in refusing to endorse IMF reform — an essential step towards giving China a voice that better reflects its economic size.

On some measures China is now the world’s biggest economy, yet it has barely a sixth of America’s IMF weighting. Two US presidents — George W Bush and Mr Obama — negotiated the IMF reforms. Yet Congress is refusing to comply. Who can really blame Beijing for striking out on its own? If the US cannot accommodate a rising China in the bodies it leads, China will create its own. The AIIB controversy is far from esoteric. It is within such institutions that wrangling over future global leadership will take place.

At times of great flux, it is tempting to reach back to history for reassurance. There is nothing new about Congress making a mess of US foreign policy. Its refusal to ratify Woodrow Wilson’s League of Nations in 1919 was more fateful than anything taking place now. America’s absence from the world stage created a vacuum that helped pave the way for Hitler. That is hardly a comforting precedent. Over the past seven decades, Congress has for the most part played a supporting role to US foreign policy. That era is fading rapidly. Foreigners can no longer dismiss US gridlock as a local eccentricity. It is imposing an increasingly steep tax on America’s global leadership.

edward.luce@ft.com

We now cease quoting Mr Luce in The Financial Times of London.

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