[toast0]

Depending on the origin country, there's a non-insignificant amount of people coming to the US, making a lot of money, then going back to their country of origin and building businesses or charities back home. Often with some amount of remitances in the meantime. I think that can be a win-win, but the ratios probably matter.

[Etheryte]

While this may happen to some degree, it's almost certainly overshadowed by the fact that this also quickly creates a vast wealth gap, leading to problems with housing, gentrification, etc. In other words, the people actually living there will very quickly be priced out of many markets. We see this effect to some extent in nearly every country in the world, just mixed in with all other economic activity, so it isn't as plainly obvious.