This has been the situation in S Texas (probably in many of the southern border states) for as long as I can remember. (I worked in the construction industry in the late 70s/ 80s) The difference has come in that illegals have spread out nationwide (& into at least, British Columbia) because they’re able to do so.
There is a huge problem (& there was some problem, back then) with the regulations & extra hoops that small business owners have to/ had to jump through. Small business has been under a multi-pronged assault for a long time.
And you make an excellent point in your post after that wrt to illegals (& some owners) wanting things to remain ‘under the table’. I’d say that is spot on.
The whole thing is delusional- unrealistic at best. A vicious cycle. Which is why Eisenhower’s approach was correct.
1 story told in the deep South is that many of the illegals found work in the construction trades in/around Atlanta when Atlanta was building to host the 1996 Summer Olympics.