As a Pole I can say that our two countries had a difficult history. Some of it good some of it bad. Russians killed many Poles, many Russians were killed by Poles. But on the whole I would say that both our peoples are very close (if not for the stereotypes). And that's the point of MW2. It's very antiwar in my opinion. Of course it makes war out to be cool and fun, with gadgets, new weapons, special effects high speed chases. If you stop for a moment and look past the graphics and the action you see the dead bodies lying in the streets, the burns, the wounds, the property damage. In MW2 everyone is guilty, every nation portrayed has done something questionable in the name of a "grander" cause. But also members of those nations have done some good things. The game shows us that behind monolithic nations stand people, people that make decisions, take actions. Sometimes good, sometimes bad. There's no clear cut difference that Russians are bad and Americans are good or vice versa. MW2's main antagonist is American after all (at least in my opinion).
I have to agree that the US Ranger parts are overly positive and idealistic in nature.