People always make this case, if you're not satisfied then move. As someone who has changed countries twice and continents once, I can attest it's not an easy or convenient thing to do. Money or lifestyle is one thing, but you're also leaving behind family and culture. Statements like these are so dismissive to that struggle that it's almost offensive to me.
The point is that middle class Americans can become middle class Europeans, but middle class Europeans can't become middle class Americans, because they can't afford it.
I didn't say it'd be easy. I'm just pointing out that only one of the two groups being discussed has a real choice in the matter.
No one said it was easy, just that it's possible, saying this as someone who's also moved continents.