Anything that affects that relationship has resonances for us in Ireland. We need our friends on both sides of the pond and we need them to talk to one another in a civil manner.

At the same time, Mr Trump appears to be mesmerised by autocrats and dictators, from Vladimir Putin in Russia to Kim Jong-un in North Korea.

It is all too easy to dismiss him as no more than a vain, delicate, unhinged, chaotic, unpredictable, comical buffoon to whom we should pay as little attention as possible. But the reality is that, as US president, he is one of the most powerful leaders on the planet. That means he must be endured and not ignored. He is, after all, the choice of the American people, whether we like it or not.

That makes his conduct on the international stage as worrying as it is strange. His contempt for European allies poses an increasing threat to world order, economically, politically, and militarily.

Thus far in his presidency, his pronouncements and policies are such that they threaten a global energy crisis, war in the Middle East, and the safety and prosperity of the few US allies that it has left.

Mr Trump has been engaging with Nato leaders in Brussels, mostly to handbag them into providing more money for the protection of Europe. His argument that the American taxpayer is unfairly paying the lion’s share of Europe’s defence is well founded, but his attempts to persuade other European members of the alliance to cough up more floundered after he started his visit to Brussels by launching a ferocious verbal attack on Germany at the start of the Nato summit. He said an “inappropriate” gas deal with Moscow made Germany a “captive” of Russia.

Earlier, European Council president Donald Tusk asked Mr Trump to stop berating Nato allies over military spending. Mr Tusk said: “Dear America, appreciate your allies. After all, you don’t have that many.” The message doesn’t seem to have got through.

It is unlikely it ever will. Mr Trump has form when it comes to insulting America’s friends while attempting to seduce its potential enemies. The Brussels summit follows an acrimonious G7 meeting in Canada last month during which he called the prime minister, Justin Trudeau, “dishonest and weak” and refused to sign an agreed joint communique.

All of this signals a deepening rift between Europe and the Trump administration over a range of issues, from the Iran nuclear deal to Mr Trump’s protectionist trade policy to the Middle East and climate change.

It is time Mr Trump learns who his real friends are.