Would you mind explaining which charges you'd get hit with? As a non-laywer, trespassing and entering (not breaking and entering, since you didn't break anything) are the only charges that would make sense to me in that context.

If the intent is there, then Attempted Burglary would be the charge in California at least. Penal codes; 663, 459.

http://law.onecle.com/california/penal/663.html

http://law.onecle.com/california/penal/459.html

Most of the US has laws that define B&E like the CFAA defines hacking.

"unlawful entry" is usually the common denominator.

https://en.wikipedia.org/wiki/Burglary

just trying to break into a building would likely be classified as burglary

From wiki: " or loitering unlawfully with intent to commit any crime, not necessarily a theft – for example, vandalism."[1]

[1]http://en.wikipedia.org/wiki/Burglary#United_States