Why not hire Americans? I went to a no name state school with a large CS class. Sure we're not MIT/Stanford quality (well many where) but plenty of talent to go around.
Whether they want to work for your wages is the real issues.
If they pass the interview then we obviously gladly hire them. But competition is hard.
We do have quite competitive wages. But we need more people than the American-only portion of the market has to offer. Competent foreigners make up a sizeable part of the applicants, and those who don't already have visa or green card we just can't hire. It's as simple as that.
you've made multiple comments in this thread about being unable to find American workers. I'm currently looking for work but looking at your profile I can't find your company. Where can I apply to whatever job openings you have?
Whether they want to work for your wages is the real issues.