Then, for good measure, Trump added a dose of boorish bad manners. He arrived late for every important scheduled appearance — so late for his speech in the General Assembly on Sept. 25 that the staff had to fill his spot with Lenín Moreno Garcés, the president of Ecuador. Moreno spoke from a wheelchair, and this abrupt change of precedence required that the podium be hastily reconfigured.

In the Security Council, Trump appeared more than 20 minutes late for a Sept. 26 meeting he was scheduled to chair. Noticeably, some diplomats turned their backs to him as he and his entourage strolled into the chamber. He was also late for a lunch on Sept. 25, for government leaders hosted by Secretary-General António Guterres, where Trump and Prime Minister Justin Trudeau of Canada avoided each other for most of the lunch, although their tables were side by side.

By then, Trump had made it abundantly clear where he stood on the vision and values of the UN. In addressing the nations of the world, he declared that America chose to stand alone.

“America is governed by Americans,” he said. “We reject the ideology of globalism, and we embrace the doctrine of patriotism.” On the International Criminal Court — a target of John Bolton, the US national security adviser, since its creation in 1998 by an international statute that the US signed but never ratified — Trump called the independent court “an unelected, unaccountable, global bureaucracy.”

This farewell to globalism, whose practical value to humanity’s future was eloquently defended by Guterres in his opening General Assembly speech last week, disregarded generations of growing American involvement with the rest of the world — more young people studying and living abroad, more US government exchange programs in many fields and that symbolic photograph of John Kerry at the UN in 2016, signing on to the Paris climate agreement with his eye on the future and a granddaughter of his crooked in his arm.

“At one level, presidential bombast is greeted with derision — and perhaps the U.N. needs more laughter. But at the same time the president chooses a Security Council meeting to accuse the Chinese — the Chinese! — of meddling in U.S. elections, as the Europeans are hammering out guarantees with them and the Russians for Iran in the wake of an American withdrawal from the nuclear agreement. Washington decides to try starving Palestinians into submission by halting its funds for the U.N. refugee program, and Arabs and Europeans work feverishly to line up alternative funding for UNRWA.

“At this General Assembly the outlines of a new policy of containment became visible — this time not containment of Stalin’s USSR, but of Trump’s USA,” Laurenti concluded.

Many speakers in this year’s General Assembly opening debate have been critical, directly or obliquely, of this extraordinary US policy of disengagement. The French president, Emmanuel Macron, spoke of a world in a deep crisis that was not an “interlude” in contemporary history that can safely be ignored. He sees the emergence and spread of a “survival of the fittest” approach, when every country makes and follows its own laws.

“What I am saying is that this path of unilateralism leads us directly to withdrawal and conflict, to widespread confrontation between everyone, to the detriment of all — even, eventually, of those who believe they are the strongest,” Macron said in a passionate speech. He later apologized for pounding the lectern.

Hassan Rouhani, the president of Iran, who is on the receiving end of very harsh charges by Trump, said at a news conference in Tehran after returning from the UN: “What’s important is that today, other than one or two countries, no one is supporting America. It is a historic political isolation that is rare for America.” In his General Assembly speech, Rouhani remarked that Trump’s decision to withdraw from the 2015 nuclear deal stemmed from “a weakness of intellect.”

Trump in his UN speech had blasted Iran as the biggest supporter of terrorism in the world, whose leaders “sow chaos, death, and destruction.”

All five other parties to the Iran agreement designed to prevent Iran from developing nuclear weapons — Britain, China, France, Germany, Russia and the European Union — have vowed to stay the course, despite threats from Trump and his secretary of state, Mike Pompeo, against those who do not follow American-imposed sanctions against the Iranians.

The threats were meant to sound alarming, just as the Europeans, Asians, Africans and Latin Americans are now beginning to exert independence and maintain distance from the US — if that is even possible.

For those in the US who have said Trump’s international tirades should be considered mainly intended for the consumption of American voters, that is no excuse — or not a good-enough reason — for ignoring how the just-ended, mean-spirited performance by Trump and his hard-liners at the UN is playing out around the world, where the US may no longer be trusted and allies may soon be harder to find.