They are only treating the symptom and not the cause. Until they address the cause it will never get better. The question that they are not asking or probably not wanting to ask is why do people take the risk, travel to the USA (and Canada) as undocumented workers?
I suspect that once they ask that question they will get answers to that question that they don't want to hear. It is probably many things why they come, but, the simple answer is that life here is a lot better than where they come from. If they start to determine the root cause then maybe they can help address those issues.
The other problem is people keep saying 'they are stealing jobs'. Well people, how many of you are willing to work the hours they work, in the conditions that they work in, for the pay they are making for little to no benefits and no pension? I am willing to bet most people won't. If they don't then guess what, the price of the things you buy will go up as they have to pay a lot more for labour, or, if you don't want to pay that price you will import more from countries with a lower wage. Either way the regular person will pay the price. The rich & powerful won't, they never have.
There will also be others that say it isn't our problem, I disagree, it is our problem. The best quote that sums it up was by Charles Dickens in A Christmas Carol. The section where Scrooge's partner Jacob Marley visited and when Scrooge said:
“But you were always a good man of business, Jacob,” faltered Scrooge, who now began to apply this to himself.
“Business!” cried the Ghost, wringing its hands again. “Mankind was my business. The common welfare was my business; charity, mercy, forbearance, and benevolence, were, all, my business. The dealings of my trade were but a drop of water in the comprehensive ocean of my business!”Those two short paragraphs sums up things on how we should be looking at this and helping out our fellow man.