The U.S. Congress and the President seem to be at a loss on how to deal with the problem of illegal immigration.
Using the military to secure the border would create a massive perpetual expense.
Treating illegal immigrants as felons would also create a massive perpetual expense. In order for this to be an effective deterrent, there would need to be hundreds of thousands of illegal immigrants put into federal prisons.
A more practical approach would be to hold employers responsible for employing illegal aliens, with progressively more severe sanctions after repeated infractions.
The reason that the feds are reluctant to get tough on employers is because the employers can claim with some credibility that the immigrants all appear to have valid documentation. Apparently, the documentation is easy to counterfeit.
The documentation for legal immigrants needs to be made more secure with a database that can be checked by any employer with an employer identification number required for making payroll tax deductions.
Although a large scale effort to make employers accountable would create expense, large fines would bring in revenue. There is no revenue to be gained by beefing up border security or by imprisoning immigrants.