It's not just the break. There are power shots that you can't even think about shooting in C8ball and any table that has round pockets. So, if you rarely shoot them and/or those shots are lower percentage in the main games you play, they'll be deficient on American pool tables. Clearly, one of the reasons why Dennis and Shane are always mentioned as "the best in the world" in American pool is their ability to make power shots so simple (among all the other things in American pool).
Potts is an amazing tactician and phenomenal potter. But, the world's greatest putter won't win on a pro golf tour that requires you to have the world's greatest long game.
Could he get there? Power play isn't just about practice. It's a change in stance and philosophy. Sure he could there. But, that'd be quite a shift.
Freddie <~~~ IMNSHO