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 an 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. Heads of family, state,...