WHEN HIS MOTHER BECAME PRESIDENT, ALEX CLAREMONT-DIAZ WAS PROMPTLY CAST AS THE AMERICAN EQUIVALENT OF A YOUNG ROYAL. HANDSOME, CHARISMATIC, GENIUS–HIS IMAGE IS PURE MILLENNIAL-MARKETING GOLD FOR THE WHITE HOUSE. THERE’S ONLY ONE PROBLEM: ALEX HAS A BEEF WITH THE ACTUAL PRINCE, HENRY, ACROSS THE POND. AND WHEN THE TABLOIDS GET HOLD OF A PHOTO INVOLVING AN ALEX-HENRY ALTERCATION, U.S./BRITISH RELATIONS TAKE A TURN FOR THE WORSE.