Reading this, and seeing the plot holes, I have a feeling the videogame industry is filled with too many people who take themselves to be too important, but don't know how to create stories that make sense.
Modern Warfare 2 needed to make World War III happen, so they felt that being "more epic" was what mattered the most. So, the end result... let's have an invasion of America, and think of whatever might work, to get it there... even if it doesn't make any sense. By the time you figure this out, you will have bought the game, and played through it... and we hope you are into multiplayer, so you will forget all about it. All that matters it that videogame fanboys will feel that it is beyond epic, nevermind the plot holes (plug in my shot at MGS4 here).