Dozens of diplomats filed into the Liberator Simon Bolivar Room at the Organization of the American States on Jan. 24 to intensify a political earthquake that could upend Latin American politics and, perhaps, the conventional wisdom about President Trump and his administration. The location was appropriate. That morning’s assembly, in a space named for the man who secured Venezuelan independence from the Spanish Empire, would seek the liberation of the Venezuelan people once again. A day after Trump recognized a young lawmaker as the legitimate interim president of the oil-rich country, the United States, with 15 other countries, signed a statement denouncing the regime of Nicolas Maduro, Hugo Chavez’s disciple and successor. In another detail rich with symbolism, the message was delivered not by an American but rather the ambassador from Argentina. Visible deference to a Latin American leader might seem out of character for Trump, but it actually typifies his approach to the crisis. American diplomats, senior OAS officials say, sought to avoid reviving “all the historical demons” of U.S. intervention in Latin America. They did so in an effort to help exorcise one of the region’s homegrown demons. Trump’s decisive support for the move contradicts his reputation as an isolationist or an instinctive enemy of multilateralism, easily manipulated by China and Russia. Most of all, allies and even staunch critics of the president agree, America’s role has been handled with nuance and care....