A migrant doesn't care if the country he is moving to has a million, 10 million, or 100 million people. He cares that it offers the job opportunities/welfare programs he wants. If Mexico was the same population of about 100 million and the US had 33 million instead of 330 million people but was just as wealthy, would a single Mexican illegal alien be dissuaded from attempting to sneak across the border? Of course not.

>Americans are obviously very unlikely to move anywhere, and not least because they don't know very much about the outside world, let alone speak a foreign language.

No. The same disparities exist with Canadians, Britons, and Australians vis-a-vis Americans. The dataset I link to in the discussion shows that, on a per capita basis, [a Canadian is 27 times more likely to move to the US than an American is to move to Canada](https://np.reddit.com/r/MapPorn/comments/6lin9k/reupload_pop...). The per capita population flows between, say, Canada and Australia are much more normalized (that is, close to 1:1)

>You need a pretty high salary in SF for example if you want to enjoy the lifestyle of a nurse or street sweeper in Copenhagen.

Ah yes, as we can see from the massive flow of Americans moving from San Francisco to Copenhagen to work as nurses and street sweepers.

>But my point still stands, unless you are already well off, or an academic, you are very unlikely to have better quality of life in the US than here.

I repeat: Why don't you ask those who actually vote with their feet? Their answers are quite clear, to anyone who looks at the data.