I think you're totally right about the permanent underclass thing. And it has been for a long time. This week I was looking into the history of education migrants' kids in the US. Our current stance of educating kids came from Texas passing a law in the 70s to strip state funding for schools which chose to enroll the children of undocumented people. (Another case of Texas using its state power to bully people; it's always fucking Texas). That law was challenged and in 1982 the Supreme Court ruled against it; Judge Brennan wrote an opinion specifically citing the creation of a permanent underclass of illiterate people not fit to contribute to any country. He called it "bad public policy." It was crazy to see like, reasonable ideas about society come through in a supreme court ruling, that's a long time past.

I think it could be viable to lock up/fine into oblivion employers hiring migrant labor specifically to be abusive/cheap. But of course a lot of monied interests would be against it. America always seems terrified about scaring corporations off. And it's so much easier to blame individuals and have them internalize the pain than to deal with the systems which set the situations.