The foreign trips of U.S. presidents, especially Barack Obama's, are rather like the tours of a rock group. There's the ridiculous entourage and onerous security measures, of course. But just as a lead singer always boosts fans' self-esteem by telling them their hometown is the best in the world, American presidents likewise cannot set foot overseas without emphasizing the importance of the country they are visiting and the specialness of that country's relationship with the United States.