[rayiner]

You want the number to be small enough where the cultural and social impact of immigrants is controlled. We don't want America to become more like India or Bangladesh or places like that, so we need to keep immigration low enough where the native culture overwhelms that of the immigrants.

According to a 2021 Cato survey--which is a pro-immigration outfit--the median response to "how many immigrants should be allowed each year" was 500,000: https://www.cato.org/sites/cato.org/files/styles/aside_3x/pu.... If we enforced that number long term, we'd probably end up with a foreign-born population under 5%, as we had in 1970. That seems like an appropriate number to foster cultural homogeneity and a high level of social cohesion.