Immigrants will be propping up Medicare and Social Security because native born Americans aren't cranking out enough kids to replace all the old people. This is why the United States isn't facing 'demographic winter' like most other industrialized nations are (Japan has it the worst), and it's not just welfare for old people that is imperiled by an aging population.

Immigrants also show up as adults and go right to work, if you don't count any kids they bring along.

I think we're in agreeance that there needs to be an easier way for regular working stiff immigrants to come over, rather than only letting in rocket surgeons or whatever. People wonder why illegal border crossers don't "stand in line", and the main reason is that there is no line for them to stand in.