So instead of deporting 20 million people, we can just arrest, try and lock up the 5 or so million who employ them. Not hardened criminals, mind you, mostly otherwise law-abiding small business owners, the guys who sponsor Little League teams and join Rotary. Oh yeah, Americans will be completely behind that plan. /s
A book called "Reefer Madness" came out a few years ago, on the underground economy. Very worth-while reading. While I agree with building a wall and/or using the military to keep potential terrorists and other criminals out, our economy is too dependent on illegals to not have some sort of "guest worker" program. (And I agree repealing the minimum wage and every other worker-related reg might help too, but we need to be realistic.)
If you want to solve the problem, that's what you'll start doing.
Of course, you'll never have to do that to 5 million business owners, as once you start doing it, most will ensure they don't hire illegals as they don't want to be put in jail.
As it is now, all business's know that there is zero enforcement and they can hire anyone they please.