You are correct about Russia.
The other world powers are not directly involved, but Russia hast to roll 2D6 every turn at the start of their turn. This determines special events in the world that affect the war. For example, one event is that the world powers meet with Russia and if Russia doesn’t attack that turn, they get 10 extra IPCs that turn.
This is a fictional conflict, but it is supposed to take place post WWII. In fact, every country starts with long range aircraft and rockets (from the original A&A rules).
I have to say this “expansion” is a delight! Currently I am working on seeing how compatible it is with the G42 rules. Since the “copyright” on this is from 93, I’m pretty sure this is public domain now. I’m heavily considering scanning in all of the components and making the files available on Boardgame Geek.