One of the things that massive illegal immigration has killed is the career ladder, from unskilled jobs upward to better paying jobs. What you have now is essentially three worlds: agricultural, meatpacking, or construction jobs that go only to illegals; checkout workers at the Supermarket or McDonalds that go to teenagers; and fancy jobs that go only to those whose families could afford to buy them a super college education.
It used to be that anyone could start at the bottom and work their way up. Now there are a whole lot of missing rungs, and a gigantic welfare system to warehouse all the people who never got started on the way up.
I don't think state or federal government, business (large and small) or many others want the flow of Mexicans or OTM's to stop. To the governments - it's just more tax base via working age persons. To the businesses - it's just more cheap labor that includes the side benefit of persons that are in a weak position to complain or file suits about pay and safety etc.
Like I said - the people in a position to make law changes or to enforce existing laws likely have a vested interest in the status quo. If you can't beat them - then join them? Deep down - I feel that our national leaders are intentionally allowing the illegals to come here to pad a slowing birth rate to shore up our supply of working age persons because we are going to need them when the baby boomers are gereatric and into the future. Europe has done so with all sorts of Mideastern, North African etc. I - personally would take a Mexican any day rather than what Europe is getting.