Europe and in recent years Eastern europeans have really shown to be top class fps players, sweden seems to produce consistently top fps players.
Why are people mentioning korea in this thread? Sure they dominate RTS, but seem lacking when it comes to fps.
In fairness the game is horribly broken, every update for css/tf2 seems to brake something new in dods :( should go back to 1.3, you forget how awesome the goldsource engine is when you've been playing on the source engine for a while.