I suppose it’s understandable that so many Europeans are taken aback by American isolationism, but other than the swiftness of its return, we really shouldn’t be. It’s merely a return to form; the default US setting of “stay out of it”. The last few decades of American engagement have been an aberration, not the norm. The US delayed entering the First and Second World War because they believed the deadly struggles on the continent were “none of our damn business” (Woodrow Wilson, US president 1913-1921).

They only threw their lot in with us in 1917, after nearly four years of stalemate in France, because Germany was stupid enough to start sinking American shipping with submarine attacks. God knows how much longer we’d have been stuck in the trenches otherwise. And there is still much misunderstanding today about why Franklin D Roosevelt committed his country to war in Europe in December 1941, more than two years after the Nazis invaded Poland. “Pearl Harbor” is the glib answer. No, not really.

Japan’s treacherous and stunning attack on the American Pacific fleet (“a day that will live in infamy” – Roosevelt) certainly sparked a US-Japanese fight to the death and ushered in the atomic age. But even as those US ships were still sliding to the bottom, America had absolutely no intention of getting into a fight with Germany. Washington’s eyes were firmly fixed westwards and on the Pacific theatre.

Their new war would be with General Tojo, not Adolf Hitler.

Few now remember that it was actually Hitler who first declared war on America, four days after Pearl Harbor. The US would never have joined the war in Europe, thus saving our bacon (Churchill described the day Roosevelt phoned him to confirm the decision as “the first good night’s sleep I enjoyed since 1939”) – if Hitler had not been so suicidally reckless as to needlessly provoke America, forgetting or dismissing the lessons of 1917.

So much for relatively recent history. The point is that America is, by nature and instinct, isolationist.

I’ve just come back from 10 days there and I cannot tell you how many decent, kind-spoken and friendly Americans I met who made it crystal clear in the politest terms that, as far as Ukraine is concerned, from here on in, the UK and Europe are on their own.

Even Democrats who wouldn’t dream of ever voting for Trump thoroughly approve of his stance on this. That at least is in part due to US taxpayers’ longstanding, simmering resentment at stumping up for our defence. One New Yorker made the point especially pithily to me.

“It’s like we’re the only guys on the block paying for private security patrols. The rest of the folks living there get the benefit, but just won’t chip in. We’re still your neighbours, but we won’t be taken for suckers any more.”

Justifiable rancour coupled with instinctive isolationism. It’s only a wonder it’s taken quite so long to come to this.