In a long, rambling address that was by turns bombastic, aggrieved and self-congratulatory, President Trump pronounced last rites on American leadership of the liberal democratic order forged by the United States and its allies after World War II. Mr. Trump used a keynote speech at the World Economic Forum in Davos on Wednesday — a pilgrimage site for adherents of globalization — to assert that the United States was done offering its markets and its military protection to European allies he derided as freeloaders. And he vowed to advance his trade war. He characterized tariffs as the price of admission to a land of 300 million consumers. "The United States is keeping the whole world afloat," Mr. Trump said. "Everybody took advantage of the United States."