Britain has lost its way and is having an identity crisis, says the New York Times. Just as Dean Acheson’s barb that Britain had lost an empire and not yet found a role hit home in 1962, so did an article last week by Steven Erlanger, the paper’s diplomatic editor and former London bureau chief, claiming no one knows what Britain is any more.

The article sparked a storm on the twittersphere and hurt rebuttals in the rightwing British press. But the counterattacks missed the point. It is not a question of whether Britain still has some good universities or the gaming industry is doing well. The question is whether Britain still has real influence in the world: and the answer to that is clearly no.

As Simon Fraser, the former Foreign Office permanent secretary, said in a speech last week: “It is hard to call to mind a major foreign policy matter on which we have had a decisive influence since the referendum.” To put it even more cruelly: we have rendered ourselves irrelevant.

Just as blood goes to the stomach after a big meal, so most civil servants are working on dismantling EU membership

I work in 11 countries across the globe and no one is interested in what Britain thinks, even in those parts of the world where we had a historical role. Since the second world war, our foreign policy has been built on two pillars: Europe and the transatlantic relationship. Both are now broken, one by us and the other partly by circumstance. We are no longer able to build a coalition in Brussels behind our foreign policy objectives. No one wants to be seen to be working with a member state about to depart. And no one seriously believes that Donald Trump is sitting in Washington waiting for Theresa May to advise him on what to do on North Korea – as we were able to do with President Clinton on Kosovo.

Even if we did still have influence, we don’t have any attention to spare for the rest of the world because all of our efforts are going into the destructive process of Brexit. Just as blood goes to the stomach when you have a large meal, so most of our civil servants and diplomats are working on dismantling our EU membership rather than on maximising our influence around the world, – and paradoxically we are taking on thousands more to do so in the pursuit of less bureaucracy.

We can’t even get the negotiations with the EU right, even though that is supposed to be the government’s principal objective, because cabinet ministers cannot agree on what they want the end state of our relations with the EU to be. Our interlocutors in Brussels are giving up because they have nothing to engage with. And meanwhile the Brexiters are gearing up to blame the Europeans and our own quisling civil servants.

The foreign policy ministerial team is in crisis: the international development secretary resigned over an ill-advised private venture in Israel; and the foreign secretary should have resigned, having apparently failed to read his brief and thereby possibly landed a British mother held in Iran with a longer jail sentence. Our politics is in turmoil, the prime minister powerless, the minority government on the verge of extinction. The cartoon sequence of teetering on the edge of the cliff is likely to continue until Jeremy Corbyn goes down in the polls, because only then can the Tories risk an election.

Britain has historically been the strong and stable democracy in Europe on which others – both the Europeans and the US – could depend. In the first world war, in the second, in the cold war and in building a liberal, free-trading and open Europe, we played a central role. We took pride, as Douglas Hurd put it, in punching above our weight. Now we have taken to punching each other in a polarised and uncertain country. Italy appears more politically stable, and France far more internationally relevant.

What puzzles our friends and erstwhile allies most is that all of this is self-inflicted. We didn’t have to give up the two pillars on which our nation has depended for so long. And we didn’t have to do so when we had nothing with which to replace them. So Erlanger’s judgment of our state of introverted irrelevance is, if anything, an almost British understatement of the sad position in which we find ourselves.

• Jonathan Powell was Tony Blair’s chief of staff from 1995 to 2007