Sorry Russell Salsbury, but this is nonsense.

The reason you and I enjoy the prosperity we have in the U.S. is because of trade. And a big chunk of that is international. Sure, America is a big country with a big domestic market, but if we are going to restrict ourselves to that then we would all take a substaintial hit to our well being. Contrary to your suggestions the supply of materials and products would be less secure should we be rely solely within our walls (eg. Florida has a freeze and California a fire and we can't buy OJ from south America?)

Your suggestion would at least double yours and my costs of living. But apart from that, there are security reasons for trade links with other countries. Also, without these international connections (that come from doing business) we can certainly kiss goodbye controlling climate if America retreats behind walls.