Hey,
There are quite a few EU guilds on the american servers.. I've been in two,
"European" Devils on Elune (
http://portal.european-devils.com/)
"The Spirits Within" on Archimonde (
http://www.thespiritswithin.org/)
And I know there are plenty more.. Used to be pretty easy to find in the wow guild recruiment forums, by searching GMT or offtime.
But I only play on my european characters now.. A real pain that they don't allow transfers. :\