For many, the US is still the land of opportunity.
For those that come obeying the regulations, they usually bring a great deal of fortitude, ingenuity and personal drive to succeed. We sometimes see them rise where those of us born here tend to fail.
For those that come across slipping through the system, their opportunity is to work whatever jobs they can find. And they do find them. They're hard workers.
There is a segment that comes for the benefits. Regardless of what the regulations claim, they receive medical benefits. I don't know if they vote or not, but many claim that they do. I've seen the medical benefits happening though, at least in California.
Farmers in our area (Arizona) protect their workers and provide for them. It's just part of the way things work. Same in Texas, New Mexico and California. Many properties have a single-wide put on their properties specifically to house these workers. Some hire them for their farms, while others have them helping to maintain their property. This is common in the country and in some very nice neighborhoods.
All this points to the breakdown of the entire "system". For those complaining, the problem isn't the borders. The problem is partially their own illogical and perhaps biased thought process; and/or it's the welfare system that makes being here such a huge benefit for poor people who know how to get into it. Eradicate welfare and you'll lose most of your argument.