“Business owners trading in a market where all their competitors are cutting costs with illegal labor must do likewise, or close up.”
This is where across the board enforcement is necessary. The notion that “everybody is doing it, so to remain in business, I have to do it too” has to be dealt with effectively by the Fed Gov.
You realize how "it" is done? Firms go to bid on available work, and just one who knows he can get labor for what amounts to slave wages, including paying "under the table", thereby avoiding payroll taxes, withholding, and all the other artificial rent streams that feed the feudal lords of FedGov, that firm can always bid lower than all the rest that run 100% above board. The honest ones must either go along to stay alive, close up, or eke out in subsistence mode with nearly indigestible costs.
The problem is not just enforcement. The problem is that government IS the problem, in several different ways at once. It does what it should not be doing (since nobody is allowed to question whether it should be harvesting the substance of "free" citizens as if they were penned cattle), and it does not do what it should (deal with foreign governments, secure borders, etc.)
Government "of the people, by the people, for the people" has not properly existed in this country for longer than I've been in it.