Escape goats and demonization of an group of people so you can blame all your problems to the wrong source.
This is just a basic math example
If there is 12 million undocumented people in the country and they spent $10 dollars a day (which is LOW for daily living) how much money are you collecting in sales tax only?
That is only if you thing that people can live in USA expending only $10 dollars a day
So even if they paid only sales taxes, that is a lot of money, then you wonder why the goverment think is a bad movement to loose 12 million revenues. IMO