From a reader:
Jonah,
It should be mentioned that Japan shares a border with nobody and Sweden shares a border with Norway and Finland, both countries of similar prosperity. The US is unique because it shares a gigantic border with a nation that has one of the worst standards of living in the west, while the US has the best standard of living in the west. If Mexico shared a border with Japan or Sweden, they (Japan and Sweden) would have an illegal immigration problem, plain and simple.
This actually reminds me of a friend of mine’s response when the comparison of Japan to Iraq came up in an argument about nation-building. He said, “You know, it helped a lot that Japan was an island.”