Once again you people amaze me...
You cannot generalize Americans based on the survy of some late night talk show host who goes out and asks questions to people. The entire purpose of that clip was to make people laugh at the stupidity of others. Yes, if I saw that clip, I'd find it quite humourous, but it does not represent Americans as a whole. It is completely ridiculous to sterotype and generalize America by a simple joke. Yes, of course there are stupid people here. THERE ARE STUPID PEOPLE EVERYWHERE! The fact is that the people who were interviewed, at least the ones that they showed, do not represent the average American.
There is a show that I watch called "Street Smarts", where two contestants compete by choosing which person they think will miss or make a simple question. Before the show, the host goes onto the street, and finds fairly unintelligent people, and askes them questions similiar to the ones you listed. The point of this show is to poke fun at the stupidity of some people in America. The key word there is SOME people. "Some" specifies a minority.
In fact, America has a great education system. Pretty much, when a student reaches Highschool, they choose classes that they find interesting, and will most likely fall into a career asociated with that class. Some people, who don't put random knowledge as a high priority, learn the things that they will actually use in life.
Personally, I enjoy learning random knowledge, even after school. I'm the kind of person who watches Jepordy and gets most of the questions right... Even before Ken Jennings (American Joke)