A lot of people think UK'ers are rude. It's weird. I only say that because I am Canadian and I have found the rudest people on the planet are the majority of Americans and people 1st generation Asian (Vietnamese specifically). I say majority of Americans because I have spent time in the midwest, where a lot of good people reside. Friendly, courteous... I say it's because they are so close to Canada.
I've been here 7 years and it never ceases to amaze me how self centered Americans are. The driving is atrocious. If someone cuts you off, and you just return the favor, watch them flip out.
Anyway I am not going to rant about my experiences in the US, but I can tell you that I don't see how it would be possible people in the UK to be ruder than people in Southern California.