(In addition to what was mentioned in other comments, proving how Americans aren't all stupid,) If US Americans are stupid, why are they the world's top power?
Some people should stop being racist and too simple-minded. BTW, I think racism is against the terms of TH's (and a lot of other websites') forums.
Honestly though, I do worry for the youth/current generation (note that some of those in the video aren't part of the youth), not just in the US, but in other countries as well.
Aside from those other good reasons mentioned as to why these people were mistaken, just the heat of the moment could've made them nervous or not as sharp.