Since all the US teams speak english well, I would suggest using
www.tourney.cc . It is a good website, you can create single elimination brackets, double elimination brackets, tournaments with group stage, leagues, whatnot. really easy to use for the moderator (you would still have to get access to the servers and force clans to play).
for qehs cups, i just used a simple bracket page, because i thought many clans in europe are not maybe so fluent in english that they could easily navigate in that site.. If you think that many clans would think that registering to that site to participate is pointless, then u can also add clans manually (noone would have to register).