I'm going to be visiting friends in the USA for a 3 week period and was wondering if it's possible to move my european xbox live user profile with it's live gold subscription to an USB stick and then being able to use it on an USA region console without any problems. The reason i'm asking is that their 360 only has a silver subscription and would like to play online with them in things like the Halo Reach Beta.
You can use (and recover) gamertags on any region Xbox 360. Only thing you may have problems with is downloading region-bound DLC/content. But as far as playing goes, your good.
You should be in the clear. I use to use a USA/Canadian Account on a Japanese 360 unit (back when I still had it).