Per country limits appear to be designed to stop 'invasion' by migration. If 200 million Indians or Chinese arrived in the US tomorrow it would radically change the culture of the US. India or China may remain largely unchanged, even by such a large outflow of people.

This fear isn't entirely misplaced, IMO, considering the US history with the natives who lived here thousands of years before European migrants arrived.

They can "appear" to be anything you want them to be. The people who made those laws had more racially motivated concerns however

https://www.cato.org/policy-analysis/brief-history-us-immigr...

Thanks for the link. A point could be made that these limits remain intact for more defensible reasons, regardless of the original motivations.

That said, I don't think the current US system is sustainable or even coherent. Hopefully it can be improved to minimize harm for all involved.