I only know about VGC, really, but from what I know of the community there the Japanese players tend much more towards meeting up in friendship groups and practicing and brainstorming team ideas together, with much less focus on sites like Nugget Bridge (which is probably the most popular VGC-orientated site, there's no real Smogon equivalent for VGC). They tend to have much more.. quirky strategies than the USA and Europe. Klefki was huge in Japan but never really made it big over here, for example, and SwaggerLum was almost centralised in the Japanese metagame, compared to minimal usage outside. I'm pretty sure it was a Japanese player that invented the Divecats team, too. =P
It makes it kinda weird at Worlds where all the European and American players know each other, but the Japanese and Korean players tend to have their own little groups, but I guess that might be a language thing as much as a difference in online communication.