Five days after Chinese President Xi Jinping left Washington, the US State Department marked the 77th anniversary of the People’s Republic of China with a greeting short enough to fit on a calling card. US Secretary of State Marco Rubio’s congratulatory statement landed on Wednesday, a few hours before dawn on National Day in Beijing. It made no mention of Xi’s visit, the trade understandings reached during the trip or the meetings the two leaders have scheduled for later this year. Washington...