Most of the US is 2am. Some places are 3 or 4 (I think NYC is 4am?).
Parts of Alaska are apparently 5am and Louisiana has no official last call from what I've read.
I'm sure there are some other cities or states with late last call requirements but I'm only familiar with these ones. Occasionally in my city, there are special exceptions like New Year's Eve where bars can stay open and serve all night if they feel like it.