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.
That is the entire point I'm trying to make. You can win the argument by being pedantic about the precise thing you were saying, or we can recognize the broader implication of what you are suggesting people to do. Only economically viable means nothing when it comes to life decisions.
Why do you think that middle class Europeans can't become middle class Americans? I know more than one example where that was no problem at all. It's not like a middle class American or European could just move and then not work and just live off of their savings. They move and get a job (ideally the other way around), jobs tend to pay relative to the living cost of where you live.
That's why people compare spending power instead of how much money you earn, because that comparison is meaningless.