Unfortunately the plot is...well it's like a good "Tom Clancy" novel that has been adopted for Hollywood with all the parts that make the story cohesive left out. Lets discuss a few of these points individually and what was left out (since a game is a lot shorter in plot content than a movie and a movie is a lot shorter in plot content than a book - so really it's forgivable)
1) "Hey this corpse looks American...lets go fuck them up!"
That's right. Russians find Alexei Borodin who just so happened to be shot dead by David Duchovny on a bad day
He was shooting up civilians at a Russian airport with a bunch of thugs that talked english in the scenario
"No Russian". Let's fill in the blanks.
Alexei Borodin was an Alias for the American PFC Joeseph Allen. The Identification for this person was suspect and upon investigation revealed a very marginally hidden trail of clues that led to a what was supposed to be a high security file about the facts regarding the identity of this person. The trick was to hide the clues enough but not so well that it looked too easy to find. (I mean seriously...this by itself is a Hollywood movie).
2) "Learn, Speak and sound Russian in JUST A FEW DAYS"
Remember this is the future. Say there is an intense learning program that targets the brain more effectively than in traditional learning techniques. The problem may be that it is an expensive treatment process or that it effectively damages long term memory...or some side effect that makes it unavailable or undesirable to the general public.
Well there's another glop of stucko smoothed over.
3) "This shell was bought by a guy in Rio" - What!?
Well here's the thing (and this is ultra cool): Every munitions manufacturer (in this future) stamps each bullet with a unique identifier using say a 12 digit alpha-numeric (36 base) numbering system. A serious database like this could have benefits in crime as well in that a shell casing found at the scene of the crime could be linked directly back to the person who bought the bullet.
You pretty much have to keep saying to yourself "Oh yeah...it's the future".
Effectively there are plenty more but I don't feel like getting into them all. I have to say that one of the more brilliant points in the story is when Price sends a nuke to DC...detonating it in the upper atmosphere to generate an emp blast that disrupts all electronics. The Russian based attack, being mostly airborne, falls right out of the sky.