The contrition tour goes beyond Latin America. In China, Mrs. Clinton told audiences that the United States must accept its responsibility as a leading emitter of greenhouse gases. In Indonesia, she said the American-backed policy of sanctions against Myanmar had not been effective. And in the Middle East, she pointed out that ostracizing the Iranian government had not persuaded it to give up its nuclear weapons ambitions.

Like other leaders around the world, Mrs. Clinton’s host, the president of the Dominican Republic, Leonel Fernández, responded effusively on Friday, hailing the secretary and her boss, Mr. Obama, for their view on Cuban policy, which he said took “great courage” and could utterly transform the political landscape of Latin America.

“President Obama is paving a new road,” he said. “It is recognition of the fact that previous policies have failed. Fifty years of a policy that has not generated the originally sought purposes can be called a failure.”