Haha, yeah, the answer is... I don't know anymore
My sense is that the current BMS default is still set somewhere in the early 2000s, albeit with a reduced commitment of allied units at the start for balance. I mean, there are only 4 USAF combat squadrons (3 F-16, 1 A-10) in the campaign at the start; it takes about 30 hours for the first carrier to arrive, and some of the ROKAF units are also not active until Day 2 - and so far I haven't seen any strategic air power arrive at all, and the only USAF combat squadrons are still the ones attached to USFK. It seems to be set up for a sort of balance more than anything, probably to prevent the game from generating too many allied flights.
There's all sorts of other flavours too, both mod and default. The "Iron Fortress" scenario in current BMS looks interesting since it has a lot of other NATO units brought in.