Will adding a key from a euro-uk box to an american acount work?

I have a prophecies and nightfall American account already. I just received the Factions Collector's edition for christmas. But it appears to be the eu-uk version. Will adding its key to my account cause any problems?

I dont think it matters.In any case why dont you just try it,the worse thing that could happen is you not being able to add it, I highly doubt youll get any kinda of hacked/fraud etc problem with it.

won't cause any problems since all the territories have been connected.

You should have no problems doing that. I recently added a Factions and NF collector's edition code to me second account. The codes were from the UK versions and they worked just fine. Plus the CEs were like 10 bucks a piece for the UK versions Good hunting!

i had no problem adding a US Platinum key to my UK editions of NF and Fac.