Apparently, there has been some confusion over how matchmaking works for international users in Modern Warfare 2.
To help set things straight, Robert Bowling has posted a bit of an explanation over on the official forums.
Here is a taste:
The functionality you're asking for, the ability to connect to BEST connection rather than first available game aka quickest match, is already built into the matchmaking.
There is no need to include an additional toggle where you manually have to ask it to put you in the game best suited for your connection, that should all be done automatically without requiring you, the player, to go through an extra step to request it.
We're doing extensive beta testing of Modern Warfare 2 internally, including with our Activision partners worldwide to test instances JUST LIKE THIS. Which is why I assure you a lot of your concerns will be unfounded come launch. However, we'll still continue to monitor activity and performance for our international users post-launch and address anything that may arise.
There's more through the link.