[Imp]

I know you like to play marines hence the air but have never had a real problem using air vs the AI, that said however I rarely use it unless I can buy 6 plus planes.
Vs a lower tech opponent buy one flight of SEAD & send in at start, if your unlucky might lose 1 but they will usually get something plus give away other targets for arty. If need be send your next flight in against these once arty has hit them & surpressed them or forced them to move. Now you just have manpads to worry about but several are probably out of ammo.
Failing this save your air till 30% or more through the game & ground forces are in position or have eliminated some of the AA.

Vs a considerably higher tech opponent air is a total waste realisticly they would most likely be shot down buy that sides airforce long before reaching the AA defence or grounded to save losing them buy that side. And a few decent AA units will probably eliminate them. Just be thankful AI buys more realistic AA units rather than feilding the best its side has to offer like most players do.

The question therefore is not so much how many more ground units the AI could have bought but more its total spend on AA vs your total spend on air. Often the AI still spends less though this case the AI does seem a bit heavier than normal, though so would I vs USA or USMC