Since he famously strolled down the escalator at Trump Tower to announce his unlikely bid for the American Presidency, most foreign capitals have been wondering what to make of Donald Trump.  Is he an isolationist or someone who cavalierly threatens war?  Is he the world-renowned businessman who will make a deal with anyone, or is he someone who underappreciates long-time friends and allies?  The answer, as is typical in foreign affairs, is complicated. As foreign diplomats in Washington, D.C. navigate their relationship with the United States of America, they should keep in mind that America maintains core interests that...