US labor laws are very weak. It's part of this whole "pull yourself up by your own bootstraps" culture. I think that's very open to debate. Between specific labor laws, and certain acts that make after-the-fact remedies possible, there are over 200 laws/acts on the books. Keep in mind that categories such as FMLA laws are under the heading of labor laws.
As for salaried employees, certainly most of the time they don't get OT - however, there are exemption status tests that make it possible in some cases. (I actually was in one, back in 1994, though in retrospect it was a bad scenario)
