Or maybe they just don't like being poor and miserable. Most US cities are crazy expensive, have no real public transportation, extreme wealth divides, rampant homelessness, no economic mobility, limited green space, cultures that are materialistic, shallow, and antisocial, a dominant car culture... they just lack so much of the vibrance of many foreign cities.

I think there are a few exceptions to this, like Chicago, Atlanta, New Orleans... and maybe not coincidentally, they are also some of the poorer cities.

Rich people make shitty cultures.