WASHINGTON, D.C. — Donald Trump’s recent summit with Xi Jinping has revived a familiar debate: Would the United States defend Taiwan if China invaded?

Skeptics point to America’s competing priorities — from the war in the Middle East to operations in the Western Hemisphere — as evidence that Taiwan is slipping down the US national-security agenda. Trump himself has questioned whether Americans would fight a war “9,500 miles away,” as well as describing arms sales to Taiwan as “a very good negotiating chip.” The change in US rhetoric seemed like a gift to Xi.