That might be a nice idea but I doubt it could be done. Unless we place those troops we bring home every 10 feet along both borders armed with orders to shoot to kill, our borders could never be sealed effectively. On top of that we cannot just cut ourselves off from the outside world. There are things out there we need. I wonder what the world would look like if America stopped acting as the world's police force. We all know the UN can't handle anything themselves. The middle east would quickly become a nuclear killing field and other things I can't even imagine would occur around the world.