By the way, it is much, much, much easier for an American to emigrate somewhere (few exceptions aside), than for anybody anywhere in the world to immigrate into the US. I always wonder how Americans, who generally have a strong opinion on emigration (whether pro or against), are generally not informed on how the entire process works.

The main reason Americans decide not to emigrate, is that the US is actually a fine country and a good place to live. There are a few other good places to live, like Western European countries, or maybe Japan if you can handle cultural differences, but the difference is not that much that it would be worth of getting through all the hurdles to move there. Nearly everywhere else, the quality of life is much worse.