OH FOR CRYING OUT LOUD AND RAPE CEASERS GHOST IN FRONT OF THE CHILDREN!?
As far as I know the CS veterancy only affects your own units, not allied units.
Not only do Soviets have a little weaker vet than US, they get it quite a bit faster too. You'll have more vet3 squads running around than a US player would. And are you sure they get it faster? because my conscripts hit vet 2 at 15 kills and vet 3 at 30, which seems average for a riflemen squad.
Each level in offensive: +10% dmg, each level in defensive: -10% received damage. However, I havent found the values in Corsix, this is from my memory and I dont claim to be right on this.