Are access keys region specific?

I have a US copy of Prophecies. I'm going to purchase a copy of Factions Collectors Edition from Germany.

Does anyone know if you can add keys from other regions without issue?

Yes you can.

Has anyone tried a foreign key on a US based account successfully?

I started with an US Prophecies account in 2005 and have added Euro Factions, Nightfall and EotN. It works.

Totally appreciate the feedback and assistance. Thanks to both of you.

Works fine.