The US has benefited immeasurably from immigration
I am going to be the devil's advocate here and piss off some people, but what he is doing is good thing at the current stage of USA development.
There is a KEY WORD in the above statement has.
If you look at the US Labour statistics, there has been no REAL job's growth since 2006. Just read them very carefully and do some extra math based on job type. Real jobs are in free-fall on par with the great depression. The growth in "employment" (quotes needed) is from gig economy. People joining the race to the bottom. The Gig economy is sucking the last drop of blood from the underclass and keeping it "where it belongs" - in the underclass place.
So where does this put things with immigration. There is no such thing as "land of opportunity" any more. You cannot come from a German village, borrow one dollar from your cousin (also called Trump) and become a real estate magnate whose grandson will become a president. Instead of that, coming on a golden lottery ticket you will drop from one gig job to an even nastier gig job until you are a ready-packed meal for the radicalizator du jour. After that you end up mowing some cyclists on a cycling lane in New York. Granted, both cases are at the extreme spectrum of "then" and "now", but IMHO they illustrate the point in history where we stand.
USA is not the only one in this. The Workforce Mobility, Gig Economy and Zero Hours mantras are doing this EVERYWHERE.
In this climate, immigration without the appropriate social safety nets and putting a big minimum threshold to ensure that a large portion of the migrants succeed is not just counterproductive. It is a recipe for societal disaster.
Now, all of this has nothing to do with Trump's issues with immigration. It however coincides with them.