> If you really like the atmosphere at universities, that is cool. Put a backpack on and you can walk into any building at any university in the United States any time you want.
I would not follow this advice if your really have no business being there. Most universities in the US are in fact private institutions and this would be considered trespassing if you are found out. You might have an easy time blending in, but if any faculty (not just police, at least at my institution) asks to see your school ID, you are required to produce it.