Move to the USA?
Has there been any major MMO's developed in the EU?
Guy! The most played MMO worlwid are the Korean ones, made by and for Koreans and asiatic market.
Even the worst of them wipe on number any US MMO.
What American MMO has been a success worldwide?
Answer yourself, the solution is simple even for you. And it's curious but it happens because is mostly played outside US than inside.