Is China going to pass up an opportunity to reshape the international order? Under President Donald Trump, the U.S. appears to be distancing itself from its established role as leader of the global system. Many excitable pundits and even sober diplomats have speculated that Beijing could fill the vacuum America is creating.

I have to confess to being one of the excitable ones. I argued in December that Chinese President Xi Jinping could counter Trump “by seizing the initiative on issues including climate change and free trade.” ...