FWIW, my community is 30% foreign-born and we don't really have any social cohesion problems. I think that length of time in the country actually matters more than the absolute number of immigrants; people who have been here since they were teens are very well acculturated. But if I were to put numbers on how many new people a group can absorb per year without radically changing its culture, I'd put it at about 10% (that's like having one new person on a 10 person team hired within the last year). If we extrapolated to the whole U.S. population and assumed they were all evenly distributed, this'd be 34M people/year.
Honestly, I think the bigger problem is that they're not evenly distributed. Some places in America never change, over generations, and remain very suspicious of outsiders. Other places become 80% immigrant over a span of 10-15 years, and then they never talk to anyone outside their ethnic background. In not very long, you end up with multiple different Americas that can't relate to each other. The parable of the polygons is very relevant here:
You think you can absorb 10% of the population every year without radically changing the country’s culture? My parents are still 80% Bangladeshi even after 40 years in the U.S.
We have empirical data showing that cultural differences in everything from social trust to savings rates persist for generations. https://marginalrevolution.com/marginalrevolution/2022/09/th...
Also case in point, both me and my wife went from F1 to green card. We never worked illegally and had fully funded gradute programs. Our parents refuse to settle in the US, they have assets and families in home countries and rather live there. We haven't tried to bring in any other relatives. 3 of our siblings have also went through the F1 route, all of them fully funded gradutes, one of them left the US after graduation, other two settled and got green card.
In my case, spouses are siblings are all skilled workers, and we have not sponsored each other.
We have one kid, even he is advanced for his age in terms of reading/math.
Each legal immigrant who becomes a citizen is the root of a tree that can continue indefinitely. If you come from anywhere other than India or China, it takes about 10 years to get citizenship from when you get your H1B. It took us less than 10. After that you can sponsor family for green cards directly. That person only needs about 6 years before they can get citizenship and start sponsoring their own family members. So it’s easy to see how we went from 10,000 Bangladeshis in the U.S. in 1990 to 300,000+ in just 35 years.
That’s very easy within a few decades when you consider that the people who are sponsored will get citizenship and can then sponsor their own parents, siblings, etc. My dad sponsored six people, and he just has one brother. My mom has 12 siblings, but them and their families went to Australia following my uncle.
There are 300,000-600,000 Bangladeshis in the U.S., up from under 10,000 in 1990. Based on H1B petitions and natural growth, the population should be more like 15,000. People are bringing their entire extended families over.
For example, right now, nobody is thinking of how many immigrants come to the U.S. through family unification for each H1B worker that eventually gets permanent residency. If you open up the issue now it’s going to become a firestorm when people realize that “65,000 skilled workers a year” actually results in millions of people every year, most of whom aren’t skilled workers.