As Donald Trump marches closer to winning the Republican nomination, many Asian governments have started sketching out plans for how to engage America under his potential leadership.

Most assume that economic nationalism would define U.S. foreign policy for the first time in decades. Furthermore, Mr. Trump’s calls for key U.S. allies like Japan and South Korea “to pay their fair share” for global security efforts are viewed as a strategic bargaining chip in revising bilateral economic relations in America’s favor.