Upon examining the Juggernaut model, I noticed something. He was wearing Multicam, and furthermore, he had U.S. Army Ranger patches on his shoulders. He has no flag, however. But the presence of Multicam and Ranger patches on a seemingly Russian opponent is weird for Spec Ops.
I added that to the trivia section, and realistically, this was probably done when they were making the Juggernaut model by basing it on another model and texturing it to be the most faction-neutral for MP.
However, just for funzies, I'd like to take an opinion poll on headcanon.
Are the Juggernauts in MW3 Spec Ops:
1. Russians, simply wearing Multicam and Ranger patches, possibly to disguise themselves as American soldiers?
2. Mercenaries, possibly ex-U.S. military, working for the Russians?
3. U.S. Military themselves (specifically, U.S. Army Rangers), who work like Shadow Company and are sent to fight and eliminate Delta Force operatives by Command?
That last one could possibly explain why you were abandoned in Survival the first place! Overlord wants you dead!
REMINDER: This is simply for fun and is not serious or suggesting anything in any way