What people don't quite understand because it has been hammered into the minds of the minds of the middle class for decades now by the ruling elite is that immigration to the USA is bad for everyone involved all around, with exception of the ruling elite. Sure, on an individual basis someone immigrating from central Asia or Central America will be far better off coming to the USA, but fact of the matter is that not only are they sabotaging the local population but they are also being played and harming the source country they come from, which is the even greater damage. The brain, brawn, and bravado drain caused on source countries by the USA sucking up talent is the largest factor of mid to long term problems and failures in source countries, all while also sabotaging and manipulating the market in the destination (USA) country. I don't care what bleeding heart liberals whine and cry about, they are causing more damage than they appear to have the capacity to grasp. It's a process not unlike the damage cause by all the development "assistance" of the past century.
Additionally, what the wealthy are doing in the USA (and other places) by supporting immigration (Pro tip: republicans only dislike immigrants and illegal immigrants when they lie to the faces of their voters) is undermining challenges and competition by the middle class and even the most modest improvement for the more challenged classes. What they are doing with immigration of any kind is sabotaging market factors that would require them to pay fair wages and appropriate costs.
Sure, some will make the argument that blather, blather global market blather captialism * blather* but the fact of the matter is that the wealthy only want everything to flow one direction. They don't want global or even domestic competition and transparency for CEOs, they don't want competition at all. What they want is to rig the game, they want to change the rules as it benefits them at every single step of the way. They are nothing different than the little shit you played with in childhood, who used to change the rules as he started losing at the game or wasn't totally dominating you. What the wealthy do ... what they are ... are the people who sabotage success, they snipe progress in order to keep anyone else from competing with them; because what the wealthy hate even more than the middle class is true competition. They love fake, rigged, and manipulated competition though that means they will win with as little effort as possible.