When President Trump declared from the stage of an opulent ballroom in Saudi Arabia that the United States was done nation-building and intervening, that the world’s superpower would no longer be “giving you lectures on how to live,” his audience erupted in applause.

He was effectively denouncing decades of American policy in the Middle East, playing to grievances long aired in cafes and sitting rooms from Morocco to Oman.

“In the end, the so-called nation builders wrecked far more nations than they built,” Mr. Trump said on Tuesday, during a sweeping address at an investment conference in the Saudi capital of Riyadh. “And the interventionalists were intervening in complex societies that they did not even understand.”

He urged the people of the region to chart “your own destinies in your own way.”

Reactions to his speech spread swiftly on mobile phone screens in a Middle East where the American invasions of Iraq and Afghanistan — and more recently, U.S. support for Israel as it intensifies its war in Gaza, which is on the brink of starvation — are ingrained in public consciousness and criticized by monarchists and dissidents alike.

Sultan Alamer, aSaudi academic, joked that Mr. Trump’s remarks sounded like they came from Frantz Fanon, a 20th century Marxist thinker who wrote about the dynamics of colonial oppression. Syrians posted celebratory memes when Mr. Trump announced that he would end American sanctions on their war-ravaged country “in order to give them a chance at greatness.”

And in Yemen — another country mired in war and subject to American sanctions — Abdullatif Mohammed implied agreement with Mr. Trump’s notion of sovereignty, even as he expressed frustration with U.S. intervention.