I don't think Americans are any more idiotic than any other nation. On a one on one level, I think everyone has some knowledge that others don't and what I think is idiotic is when people don't see that. I consider myself an educated, intelligent individual, but part of that is knowing that I don't know everything. My grndmother is pretty much a black hating hillbilly, but the woman could make a plant grow in a granite mine. I have trouble keeping a cactus alive. So there is knowledge and experience there that I don't have, even though she is practically afraid of my laptop.
People tend to specialize their knowledge as well...so because someone seems dumb on camera, doesn't mean they don't know anything. I knew a guy who couldn't read, and didn't know anything about life outside of his town, but he could fix pretty much anything mechanical, and could build buildings.
Some of these people do seem a little dumber than they should be, and in fact, I think a smart person would be inquiring how many people they had to interview to find the ones answering stuff wrong. I see camera edits, and any time film is cut, bias is created. I would like to see the whole reel. Maybe the guy in the blue shirt got half the questions right, or even corrected himself after the fact.
What they don't show is more telling than what they do.