I would be offended by that if it weren't a fact that Americans are painfully ignorant about geography. However, a rare few like me actually care about the world around us.
Why should someone halfway around the world know every tiny city on Earth? I guarantee most people in Europe wouldn't rattle off Appleton, Wisconsin and Plymouth, Michigan. Don't be a prat.
The average is so high because the knowledge is so obscure most people steer clear. Because they think they probably wont get more than 1 or 2. (I think many people only tale quizzes when they estimate to get atleast half right, and some only do they quizzes they know they are good in, so where they expect 80%+)
I wonder why Umeå has the honour to be 5th most guessed. I knew the first 4 but no more. All the others are equally unknown to me. (though Lund vaguely rings a bell, but I might be imagining that ;) )