I've seen lots of video clips where an English (or otherwise) reporter takes to the NY streets and asks basic geographical or political questions and is met with dumb answers, but im sure we have our share of idiots too.
I keep in good contact with a wide range of Americans of all ages, and generally I have noticed something that the 'smart' ones have in common. Those who I would not consider to be idiots have actually visited somewhere outside of America (not including Canada and Mexico). They tend to be the better educated ones, and tend to have some clue about the world we live in. I would have to say that the average Joe Public Americans I have encountered are generally clueless, and perhaps to a degree that you simply wouldn't find in England. It would be interesting to see some questions put to some English common-folk.
In fact there's something for me to do one weekend over the summer! If I do film some questions being answered, Ill stick it up on YouTube and revive this thread and we can sigh wearily at the incompetence of our own country!