Until recently, Greenland’s 56,000 citizens went about their lives on the sparsely populated mid-Atlantic island far from the glare of international attention. Now they find themselves — and their political future — on the shopping list of the incoming U.S. president.

President-elect Donald Trump doubled down this week on his ambition to take control of the autonomous Danish territory — as well as Canada and the Panama Canal. He told reporters that he would not rule out military or…