Robert Guest writes the Lexington column in the Economist. “I’m going to talk,” he says, “about America and why I think it is uniquely positioned to be not merely the current superpower but the next superpower. I’m going to focus on one very narrow aspect of this. America’s greatest strength, in my view, is that people want to live here. That’s something that the people who already do live here take for granted” — maybe because we haven’t visited the other countries of the world and seen how much they suck?