In the recent frenzy of commentary seeking to interpret U.S. President-elect Donald Trump’s increasingly adamant comments about territorial expansion to Canada, Greenland, and the Panama Canal, too much of the discussion has focused on matters of secondary importance. These range from assessing whether Trump is merely engaging in a game of showmanship or distraction, to deciphering how those regions’ inhabitants feel about ceding territorial control to the United States, to determining how much it would cost to purchase their acquiescence. From a policy perspective, though, more fundamental matters have gone surprisingly unaddressed, beginning with the question of whether any of...