I am still not sure why most countries don't have relatively open borders. Europe would benefit from Americans, America would benefit from everyone else, grass is always greener and all.

You can see Americans wanting to move to places many people would think kind of crazy, like Latvia or China... why not just let them?

Idk, maybe I am too optimistic, but I believe global freedom of movement (or as close as we can come to that) is the only opportunity towards world peace.