UNITED NATIONS — They laughed.

Not even a minute into the speech. They laughed.

On the planet’s biggest stage, with more than 100 world leaders gathered with their ministers, ambassadors and dignitaries of every stripe, while news cameras from as many countries broadcast the speech in as many languages, they laughed.

President Trump seemed surprised when he heard it. Attendees of the United Nations General Assembly, normally a scripted annual gathering of presidents, prime ministers and wizened diplomats, do not typically break decorum, let alone laugh at the most powerful man in the room.

[The president doubled down on his “America First” foreign policy.]

But there it was, soon after Mr. Trump commenced his highly anticipated speech on Tuesday, as he bragged about how much his administration had accomplished in two years, “more than almost any administration in the history of our country.”

For Mr. Trump it was little more than a minor boast, a well-worn line trotted out frequently at rallies with ardent supporters across America that rarely warrants special mention anymore. But for some reason, at the United Nations on Tuesday, it resonated.