For decades the US has turned a blind eye to illegal immigration because of how much profits agribusiness and construction makes from it. It wasn't an Obama thing, but spanned several presidents and both parties.
Correct. But I should say Obama was being very public about the program whereas previously it had been more of an under-the-table thing. Now the question is, why hasn’t Congress made laws so agriculture and construction can benefit from cheap foreign labor in a legal way?
This seems like an obvious and workable solution. Could it be being blocked by something - perhaps unions representing local workers? (only guessing)
That's what the H-2a program is. Many employers have avoided using it because it gives labor actual rights, requires an above-minimum wage, and includes free housing. All of those provisions are currently being gutted though.
To me gutting these benefits is the less bad alternative compared to just bringing in people illegally. And also H-2A doesn’t cover construction workers.