I must argue against
Their are more than enough American addons and actually not enough East units.
Ok we have the several Nam mods around + WWII mods (in which the Americans have been portrayed the most, even though most of the war was fought by the Brittish), then we have BAS which are making mainly American addons such as their excellent Delta Force n Ranger unit as well as their Choppers. DKM make mainly American choppers such as the Comanche, however are working on the Russian Havoc. Then we have a lot of Brittish packs, as well as the numerous European nations such as Norway, Polish, Finnish etc to name a few.
Then we have a few "studios" making ONLY eastern addons such as Red Hammer, and then we have Sig who has redone most of the Russian tanks.
Now what are we REALLY missing - in regards to war going nations?
Firstly China is emerging as the US' because threat in regards to economical and millitary might. I only see the Taiwan workshop who are making a few Chinese addons. Also I must comend Sig for his Excellent modeling on the Type 98 Chinese MBT. Very accurate aestheticly, but lacks in scripting and special features such as the laser gun on top (which I dont think is that hard to do since BAS has been able to make backwash which blinds people who are underneath their Chinook who dont have goggles.
Oh in the topic of Asia, we could also add Nth Korea, who have a considerably powerful army.
Secondly Israel is a very powerful country in the Middle East and has been in many major conflicts (well in their area), and have a vast assortment of locally produced warez which would make good addons for people who wish to recreate Middle Eastern Battles.
Thirdly African nations have been almost totally disregard besides the few militia units to recreate Black Hawk Down scenes. However Afriacan maps would be the most interesting, especially in areas like Congo. Maps in which a small group of UN peacekeepers face off against hundreds of armed militia.
All in all, in regards to the original topic of USA v Russian units. The US has had numerous aircraft created, most notably the Comanche, McDonald Douglas Little Birds (think its the OH-6 or something) as well as retextured Black Hawks, CHinooks etc. Then their are all the jets. With the F1-11 on the way as well as the F-15,F-16,F1-17 and the F-18's around as well as the Harrier, the US airpower have been recreated numerously. How many Soviet/Russian aircraft do you see being made? I can only recall the Havok, as well as VITs Mig-29 Fulcrum.