Sure but let me ask you. What’s the optimal amount of immigration? Is it 1m per year? 10m? 100m? It’s fine to say immigrants provide a net benefit to society and its culture (I agree). But that’s only true to an extent.
A good rule of thumb for me is immigration is beneficial when the immigrant stands to benefit from fully assimilating to the existing culture (language, norms, abide by laws, etc). 20k Haitians in a town of 60k violates that balance.
I'll try to answer. I don't think there is a magical number but rather a range that is reasonable. But I'll note that you asked me a question about what the national number should be but go on to make a point about 20K being too much for a town of 60K. Immigration always tends to be "lumpy" in that for various reasons people tend to cluster. So we had lots of Vietnamese refugees in Louisiana in the 1980s, including a disproportionate number in some rather small towns. After an adjustment period that has turned out pretty well for the refugees and those small towns. I do think as a matter of policy state and federal governments should support towns and school districts experiencing those kinds of surges.
As for the optimal number, I think we need to look at it both from an economic perspective and a social perspective. If you look at labor force growth, the U.S. labor force grew at 1.6% per year from 1950 to 2000. Since 2000, it has grown much less in spite of high immigration rates, about 1.0% per year in the naughts and 0.5% per year in the 2010s. I'm not saying one is better than the other. Simply that we can live with both. The labor force is just under 170 million these days. If we want to juice it by 1% through immigration that's 1.7 million per year (and higher when you consider working age people will sometimes have family members who are not working age). I'm just laying out some numbers to inform the discussion. I think an overall immigration target of 2-3 million per year is something that makes sense. I wouldn't argue against something a bit smaller, but purely from an economic perspective I think that is a number that would work well for the economy.
The other side is assimilation. In recent decades we've seen surges of widely different groups. Cubans, Vietnamese, Hmong, Mexicans, Central Americans, Dominicans, Chinese, Indians, Filipinos, Somalis, Ethiopians, Haitians, Venezuelans. Do any of these groups stand out as having trouble assimilating. I don't think so. Sometimes their English is not the best. But they find jobs. And here is the kicker. Their children do exceptionally well. I don't think any analysis of the pros and cons of immigration is complete without considering how well children of immigrants do in this country and the enormous contributions they make. This includes children of poorly educated immigrants who never fully master the language. I've interacted with people from many of these immigrant communities. I've had students whose parents came here as immigrants. As dirt poor immigrants and refugees. They are ballers, no matter where their parents came from or their parents' socioeconomic status. That's just anecdotes from people I've interacted with. But there are also hard comprehensive data that confirm those anecdotes.