Donald Trump campaigned for the presidency claiming “the world is laughing at us.” Now it really is laughing — at him.

Apparently mistaking the United Nations General Assembly for a campaign stop on Tuesday, Mr. Trump opened his annual address — usually a somber occasion for a president to assess the state of the world — by boasting that his administration “has accomplished more than almost any administration in the history of our country.”

That’s when the other world leaders started chuckling.

“Didn’t expect that reaction,” Mr. Trump said, like a comic in a roomful of hecklers, “but that’s O.K.”

Actually, it’s not O.K. America’s president is now openly derided in the most important international forum.