Don’t deport them, don’t threaten to deport them.
Just take away their jobs and place to live.
No job and no place to live they’ll leave on their own. It isn’t that complicated. What’s more, is that the people who provide jobs and a place to live are Americans. They can be fined and put into prison. Do it a few times and the rest just might see the light...
Yep, lack of money and shelter always gets them. It sure would dry the problem up and quickly.