[narwan]

Hmm, I think you're reading to much into this. There are some nation specific abilites but as far as I know it's not nearly as elaborate as you think it is. It would be extremely hard to quantify and judge. Experience and morale are basically what drives the fighting abilities of a unit (besides their gear off course). So I don't know what to make of your remark that "If these codes were not there, the game play would be pretty flat knowing the Green US Troops can fight the same as Elite German troops" as GREEN troops (exp<60) obviously don't fight the same as ELITE troops (exp>80).

Country specific code elements are things like the japanese and marines 'no surrender' ability. Hmm, can't really think of another country specific ability I know off actually. Nor can I think of any special things associated with a german unit being SS as opposed to those from other branches, besides the above mentioned exp and morale scores.
Those scores do fluctuate between years illustrating overall developments.

There are bonus' to specific types of formations like the Ghurka's bonus to melee combat and (not completely sure though, I'd have to check) mech infantry getting a bonus to their armor skill score. But that's about it. If there's more it would be new to me...