Good luck getting an American to work the farm fields, or a lawn crew, or clean hotel rooms, I'm not saying thats all an immigrant legal or illegal is qualified for, but they're jobs that need done and the average American feels are beneath them. It's a problem of our own making, when a person gets enough in government benefits to not need to work, they wont.
But hunger is a great motivator, why I think there needs to be a safety net, but it needs to be more like a G-string than a hammock, just barely covering. They'll take those jobs once they're forced to put down the XBOX and pick up a lawnmower if they want to eat.