I am not sure if the differences are more cultural differences or are actually related to derby North America style. It's a little more "male" in the stereotyping department whereas UK derby still seems to be more on the "female" side. I dunno, it's hard to explain...
Here it seems WAY more common that people were involved in some kind of sports before they joined roller derby, usually in either ice hockey, rugby or
some form of skating. Very few people now join a big league not knowing how to skate it seems. These girls have been going against the grain, as it were, for years now
In most leagues who are playing roller derby "seriously" i.e. WFTDA teams, fishnets are almost mocked. I have heard many conversations at various games/tournaments where some players have judged a team or player harshly because they are "still wearing fishnets" and comment on how they were "that clueless once, thank god we know better now" because everyone wants to be seen as "serious" athletes and such (it's the norm for top teams to have full uniforms here so everyone looks the same a la Rose City etc.) Sparkly shorts have yet to fall out of favour
People in roller derby (and the fans!) are a bit more aggressive than the UK too but I suspect that is more of a cultural thing. People have absolutely no qualms about trash talk to the point of brutality, or on occasion getting into fights with other teams
A lot of teams seem to have a higher ratio of LGBT players than the UK teams (again, perhaps relevant, perhaps not due to cultural differences, how and where teams promote themselves, word of mouth etc)
Things that are the same - everyone is just as passionate and emotional about roller derby as they are back home (My home team had a meeting last week which was a lil heavy and pretty much everyone cried at some point!), everyone is still awesome and everyone loves the sport, wants to make it the best they can and want to keep skating until they break a hip!
As for the males involved in derby here, the only comment I have heard with regards to the gender thing is from our home coach. Over the last year or so he says he has realised that it takes a completely different approach to coach women as it does to coach men. With men, he can shout and scream and kick their arses them until they do what they are meant to do. If he does that with us however, we either ignore him, become demotivated, cry or just argue back so it's not effective. He has had to learn to be more motivational rather than full on and aggressive.
I can't think of anything else right now (and everything I have written above may just be bollocks but I was never very good at sociology stuffs, sorry!