American presidents have a habit of describing their Chinese counterparts in terms of awe. A fawning Richard Nixon said to Mao Zedong that the chairman’s writings had “changed the world”. To Jimmy Carter, Deng Xiaoping was a string of flattering adjectives: “smart, tough, intelligent, frank, courageous, personable, self-assured, friendly”… Donald Trump is no less wowed. The Washington Post quotes him as saying that China’s current leader, Xi Jinping, is “probably the most powerful” China has had in a century. Mr Trump may be right. And were it not political suicide for an American president to say so, he might plausibly have added: “Xi Jinping is the world’s most powerful leader.”