http://www.gamersloot.com will sell you the key and let you download the CD images, or you can just change the update.dat in your euro DAoC directory so that it patches you to the US version.
You need a US CD key to make a US account and yeah you can just change the update.dat to the US version and patch to the US version.
The other option is to go to the Herald and download the free trial - this gives you an SI account for free, then you can just buy ToA and Catacombs keys from http://www.gamersloot.com and download the Catacombs installer from Gamersloot but it is about a 2gb download.
OFFICER XEST - PROTECTING YOU AGAINST FORUM CRIME
Che Xefan, el presidente.