Just off the top of my head --
1.) There are a lot of highly skilled immigrants who do come here. Trump wants to curtail the HB-1 visa, because he thinks local IT talent are being harmed. He's wrong. The IT and tech industry have said specifically the HB-1 visa is essential to Silicon Valley and innovation. But foreign IT has helped create a lot of innovation for the United States. Dropbox, Tinder, Google, whatever. The president of Google is Indian, for example.
So, for one, the HB-1 visa should NOT be curtailed.
2.) Most economists say immigration usually help out the United States. Now with automation that may change, but honestly, menial jobs like fruit picking, cleaning hotels, etc are done by poor immigrants. They're not something that more settled (read: white) Americans will do.
Should we have criteria-based immigration visas? Yes. We should. We should have x going to various nations for fruit picking, hotel cleaning, etc and we should decide that on a neutral formula (read: not decided by Trump). We should maintain the HB-1 visa. Etc etc. Should we build a wall? No, because it's cost ineffective. Should we have e-Verify to make sure everyone in the United States is legal? Absolutely. (Note: I am a center-right conservative on immigration. More Bush 43).
I would point out that immigration has not really dented the unemployment rate since the Great Migration started in 1965. We've managed to have a very healthy economy on balance and the Great Recession was due to other factors, not immigration.
Most economists believe immigration is a net benefit to the United States. I tend to agree. I'll link an article later.
I disagree about the absolute need for H-1B visas.
There are already visas available to immigrants possessing vital skills that haven't been fraught with the documented abuse of the H-1B visa regime.
And I also disagree with the "jobs Americans won't do" argument. That categorization is overly broad -- it encloses entire swathes of the economy. It's nonsense to suggest that American-born workers aren't willing to work fast food, clean hotels (my mom was a hotel cleaner before she got her first permanent job), or do sweaty unskilled construction or warehouse work. Or, for that matter, become university professors or start engineering companies.
I concede with that few Americans undertake farm labor, but that's because Americans are more than 85% urbanized and live miles away from any farm, and a large proportion have no relatives who do. Not to mention, farm work in the US is very heavily mechanized -- most of the underemployment of the rural population stems from that fact alone.
But in general I agree with the thrust of your post. The parts of the US most adamant against immigration are the places that receive, statistically speaking, no immigration at all -- W Va, Okla, Miss, etc. Their proportion of foreign-born residents as a proportion of population are the lowest in the country. Their opposition to immigration has little to do with some theory of economy disruption by immigrant bottom-feeders.
