I think it has been shown that the population of the US would either be stagnant or declining if it were not for immigration (legal and otherwise). People are not having kids like they used to, all people, but especially WASP's. That is bad when our economic models are built on growth, you MUST have constant growth or you die, just look at Japan or even China now. I have to wonder if that is why they are letting this immigration thing happen in Europe, their population is even more negative then ours.
The government NEEDS the population to increase, and if it increases illegally, it is a win win for them. People working illegally will pay taxes into the system but don't take them out (SS, IRS returns etc.) Yes, I know you will say they receive certain benefits, and they do, but in order to keep the Ponzi scheme of Social Security and others going you need more people coming into the system.
Interesting times.