One legitimate issue with immigration is the difficulty immigrants face transfering their expertise.
I don't know how large of a problem this is in the US but I know it's a major problem here in Canada.
I was just talking to the owner of a coffee shop that I frequent almost every day before I start work. I get the same muffin and drink combo ever single day lol. He and his wife run the place as a family, it's a franchised business. I believe they are Vietnamese. At any rate I've come to really enjoy my morning greetings with them as they are such amazingly kind people. He has also always struck me as very intelligent. But I didn't learn until just the other day that he has a degree in computer science. Specifically he studied compiler design. Having taken computer science myself and knowing some of what is involved in compiler design I know that that is one of the most difficult subjects in comp sci. I didn't prod and ask why he isn't using his degree. And it may in fact not turn out to be an instance where his skills are not transferable because in this case I believe they would be much more easily.
However it does highlight an issue that many immigrants here face which is that many many highly skilled immigrants find themselves unable to use their skills because there is no process via which their skills can be properly vetted. So for example it's not uncommon to find skilled sergeons, DRs and those with PHDs driving taxis or working retail.