Need help: Eu -> us.

[[Soul Eater]]

Try changing your realmlist to this:

set realmlist us.logon.worldofwarcraft.com
set patchlist us.version.worldofwarcraft.com
set realmlistbn ""

and then, log in on your EU account , and if done correctly it will install a patch - after that, try to log onto the US account.
set portal us

[Tretabyte]

I forgot to mention one little detail
sometime when wow is loading, it will search for data folder and if it find on it "grabs" to it, so you can have the realm file pointing to US but it detects the GB data folder and grabs it
To prevent that to happen you can try 1 of 2 things, or you delete the GB folder completely (not a good way to go since you may want to get back to your EU account) or you rename it like "--enGB" or something else, just prevent the folder to be named enLANG at the beggining.

[Manisher]

Change realmlist and delete your WTF and Cache folder