Americans have never been more divided, and we're ripe for a breakup. The bitter partisan animosities, the legislative gridlock, the growing acceptance of violence in the name of political virtue--it all invites us to think that we'd be happier were we two different countries. In all the ways that matter, save for the naked force of law, we are already two nations. There's another reason why secession beckons, says F.H. Buckley: we're too big. In...