Donald Trump's visit to Beijing, the first by a US president in nine years, not only included plenty of pageantry, but produced some apparently substantive agreements. Aside from China resuming purchases of Boeing planes, beef and soybeans from the US, the two countries agreed to set up boards of trade and investment, and pledged to establish a 'constructive relationship of strategic stability'. And Xi Jinping will visit the US in September. But will this really ease recent trade and politica...