The speech also provided a made-for-Twitter moment in which a clearly parched president interrupted his broadcast to reach for a bottle of water, struggling until an aide told him where to look. And when he finished speaking, Mr. Trump ignored questions from journalists seeking comment on the sexual assault scandal swirling around Roy S. Moore of Alabama, the Republican nominee for Senate in a special election next month.

Announced with little notice and delivered midafternoon from the Diplomatic Room of the White House, the president’s speech was designed to be what his critics have never offered him: a sweeping and positive assessment of his own performance as the nation’s commander in chief and top diplomat.

By recounting his travels and detailing the just completed Asia trip, Mr. Trump sought to make the case that the United States was once again playing a leading role in the world.

“My fellow citizens, America is back, and the future has never looked brighter,” he said.

Critics say Mr. Trump has abandoned the United States’ status as a global superpower by retreating from trade agreements and backing out of the Paris climate accord. The president’s political rivals accuse him of straining relationships with allies in NATO and elsewhere while embracing despots, including President Vladimir V. Putin of Russia.

“He is so easily played by foreign leaders, so transparently susceptible to flattery,” said Eliot A. Cohen, one of Mr. Trump’s harshest critics and a former adviser to Secretary of State Condoleezza Rice. “It clearly has undermined the reputation of the United States, the credibility of the United States.”