The thing is, it's not just Americans. I was on a server once where there were a bunch of French people. They decided to gang up on me since I wasn't French, so they all joined the same team. It was 4v1. However, they happened to be terrible at the game, so I completely demolished them. They called me gay, a fag, an asshole, everything. Then they called me a noob. Now this made no sense. If someone's owning your collective asses, you do not claim they are new to the game and have no skill, which is, as far as I know, what noob means. I then proceeded to say "If I'm a noob, how come I can do this?", owned them again, and left the server. A few minutes later, my firewall blocked a poorly executed intrusion attempt. From the same IP as one of the players. They had just been owned yet again.
I'd have to say, I can't say which is more overused, but fag/gay, noob, lag, haxxor, are all overused. I think I've only said lag in one case, and that wasn't after someone killed me, it was when I join a server, go at about 2 fps, and say "sorry guys, lag, bye." In fact, insults are stupid almost all the time, and are all overused. The only insults I'm okay with are when you're obviously being playful, like "this round, I'm going to kick your sorry noob ass" at the beginning of a match. When someone kills me, I generally say nice shot, and attempt to get back at them through in-game violence, not words. Remember kids: When you get upset, kill the person, don't yell at them. It's like the opposite of the real world.