Forgive us if we missed it, but we don’t recall Donald Trump campaigning to invade Panama and retake its famous canal. But there was the President-elect on the weekend, threatening our Central American ally with punishment if it doesn’t meet his demands. “Our Navy and commerce have been treated in a very unfair and injudicious way. The fees being charged by Panama are ridiculous, highly unfair, especially knowing the extraordinary generosity that has been bestowed to Panama—I say, very foolishly, by the United States,” Mr. Trump told a crowd in Phoenix. “This complete ripoff of our country will immediately stop.”...