Considering my playtime is 11pm - 4am and I play with the Japanese mostly, did you miss the "in my experience"? No sarcasm here, I've seen more cliquish behavior from NA players than I have from Japanese players when it comes to these kind of events, even to the point they'll kick out people that helped them get their shit done for someone in their shell (that didn't even have progress done) just because it's a shell mate, this could be a server specific thing.
That's why you don't ignore what someone writes, but then again, since I can actually speak and understand Japanese that helps participating with them. So unless you were trying to say Americans are a lot more welcoming then I'm confused why you'd think it was sarcasm because in all my MMO experience and online gaming experience, I've yet to see how the JP are cliquish..unless you confuse the fact you probably refuse to learn Japanese to communicate with them as them being the ones at fault?