It's actually really ironic. Loads of US shows make fun of the stereotypical Brit, The Simpsons, Futurama, Scrubs, married with children, etc, etc ,etc, just about every one of them in fact.... yet it's to make a joke. The writers know enough about Britain (and the other nationalities they take the mick out of) to know what to highlight and what parts of our stereotypes are funny. For some reason most of the rest of the US population don't really get it... the stereotypes, sarcasm or anything that doesn't start with "knock knock" or "why did the chicken".
When I was in the US the Wife and I got to talking to a guy from Texas. He was showing off and being loud, but friendly enough. Anyway, he got his wallet out and my wife commented on the "funny looking cards". We pretended that we didn't know what his credit card was, asking about paying with plastic and how it worked etc. He believed 100% that we were in the dark ages, didn't have the internet and had no idea what a mobile phone was. The strangest thing was the perplexed look on his face when we told him we were joking, his phone was out of date and his credit card was only really of any use in 50% of the US nevermind the UK.
Fun times though