I find this comparison of American and Japanese social manners in game entirely unsurprising. That just reflects the well-known respective cultures of Japan and the US. I've played on Europe servers quite a bit, but never in game chat, I party up with a European friend. I have watched a large amount of content from European players, though, and they seem to be just about on a par with US players in regard to what you're describing. I won't mention particular nationalities, but certain European countries seem chock full of ignorant and rude players just like the US. Duos queued together especially seem prone to abuse their team mates, in languages they apparently assume the subject of their abuse doesn't understand, often referring to them in third person. A lot fewer people in Europe seem to use game chat in general, due to language differences. Just my 2 cents.
