I'd have to agree with whomever mentioned JP just having the upper hand when it comes to working as a group. Back when I played FFXI, I used to absolutely LOVE when I got into JP groups because I knew we were going to actually get things done. Their culture is based around striving to be great at what they do. They pride themselves on it, even. It's just a very different mindset than Western culture, particularly for NA. Over here, we have different priorities than JP does, which tend to focus around more capitalist ideals (generally speaking).

I truly don't think it's because NA has more 'bad players' than JP does. Like it's been said, I think it's more culturally established, and it's not something that's been limited to this game alone either.