You're kidding, right?  You do know a bill needs to actually pass to become a law?  That bill was passed by the House but never passed the Senate and was never signed by the President.  Even then, I don't see any provision in the text that makes overstaying a visa a criminal offense.  Might be wrong there, and if you'd like to point me to a particular section, I'd be happy to look at it.

By your own admission, the majority of people in this country illegally are here as a result of visa overstays, which is not a crime.  Locking someone up when they have not committed a crime (and are not suspected of having committed crime) is a violation of the United States Constitution.