Yes, it is different.
Think of it like a multi-verse, where there's the AM Universe, and the AT Universe, existing side by side, but never knowing of the others' existence.
The AT Universe more closely resembles real life and history, with the exception of The Adventure Team, and all the characters contained therein.
So, in stark contrast to The AM Universe, there are relative few fictional places and agencies. Which is good because I kind of hit you over the head with the alternate reality that is the AM Universe. This will be good to come and have a breather.
I'd like to outline some of the basic stuff, without any spoilers, because I've got some nifty photo-shoots/stories planed for the spring and summer, and I don't want to ruin it.
1964 - Enlistment, deployed to Vietnam.
1969 - Prototype Adventure Team
1970 - Official Adventure Team
Just so you guys know that this separate Universe does exist, and has nothing to do with the Action Man Universe.