I'm a brit.
I find that you can get arseholes from any part of the globe, the anomnimity (I know I've spelt it wrong) of the internet and the overly-competive nature of some online games probably creates more problem player than any factors relating to nationality.
I do notice that many people do tend to group with their own nation in some arguements in a way that could suggest an "us versus them" mentality, particularly if the arguement involves someone making a daft, more patriotism-than-fact comment. To me, most of the blind patriotism appears to come from Americans (usually making inccurate claims about their country's military, preformance in WW2 or politics, or the problems with more libberal nations), but I am very willing to accept that this is just what I'm noticing and picking up on rather than an accurate depiction of facts.
The thing that pisses me of the most is how unimaginative the arseholes are. At least come up with a witty comment. Anyone who uses a "your mum/mom" insult should be cut up for spare parts.