I don't understand immigration restrictions at all. If the US is afraid foreigners are coming to "take our jobs" and is concerned about its citizens well being, then why isn't it concerned with the fact that cheap foreign labor could save money to millions of americans while it currently doesn't, since immigration is restricted? Or if it is concerned that foreigners are going to use the social safety net without providing any value, how about not providing it to foreigners?

There's absolutely no grounds for restricting immigration. The US was built on immigrants and now somehow it is no longer a viable policy?