As far as regions go, it partially depends on the system and region encoding, but in general, the main release regions are NA, EU, JP, and AS. You'll see occasional deviations, like PC games that are exclusive to China or Korea, but for the most part, "US" isn't particularly accurate.
It gets a bit hazier as far as digital releases go, but I tend to question if indicating regions on those really makes sense, particularly since it's either not really defined (GOG.com) or could change at random (Steam). There are getting to be so many digital variations, I sometimes wish I could filter them out of search results just to de-clutter the page a bit :/