Americans? Yeah, it's always Americans. Every dirty driver I've ever met is an American.
It's probably cultural, yes, like they think ramming you off the road is free speech - they'd probably shoot you if they could and claim it was a second amendment right. Either that or they just can't drive - they just have pointless straight roads out in the country, and dumb grids in the city. And their speed limits are really low, like 55mph or some rubbish. No wonder all their motorsports are just like drive straight for 440 yards (and they can't even do that without dying, so now it's 1,000 feet), or just drive at 200mph and go left a bit for four hours until everyone else crashes.
See how that works? Yeah, don't be that guy.
Oh, all of the above is really quite obviously sarcasm, but just in case...