Well, I'm assuming that you're talking about English accents specifically (not Welsh, Scottish or Irish). We get plenty of American infomercials over here. The only one where I've heard a British accent is in the Magic Bullet infomercial - and that Mick guy is
so annoying!
I agree with eclectics - it's unlikely that many Americans will be able to place most British accents (only being able to differentiate between English, Scottish and Irish - I think a lot of non-Brits find Welsh accents to be 'English' accents), so no prejudice (except against British people in general?).
I remember the first time I went to WDW... Me and my parents were on a Disney bus going to DTD and there were two girls (they must have been late teens/early 20's at the time) on their way to TL, but a thunderstorm had just started. The bus driver was talking and the girls were saying something about getting thunderstorms in Pennsylvania, and my mother said, 'Oh, we don't get that many thunderstorms back home'. One of the girls just turned and looked and was like 'OMG, where are you from?!' - her friend was like 'uh oh...'. My mother said Britain (it's easier than saying Wales because most people not living in the UK seem to think that Wales is
in England), and the girl started screaming and kicking the chair in front of her and saying that she loved our accent and wanted to come to the UK, get the accent, then go back home to the US.