When the BBC news started playing audio of Steve Kerr, the head coach of the Golden State Warriors, I knew he wasn’t going to be talking about basketball. The NBA playoffs are not prime time news in Britain. Kerr was talking about gun violence—specifically, attacks that had just taken place in a Buffalo grocery store, a church in California, and a school in Texas. He was expressing the frustration that many people, in America and in its friends and allies abroad, feel about the seeming inabilit...