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.
You shouldn't generalize a country of 300+ Million because of stuff you see in YouTube videos online. There are many among the American populous that are very well-versed in geography.
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 must have tried Vaxjo three or four times to make sure. Kalmar too, but maybe that's just my appreciation for history leading me to over-estimate its population.
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 ;) )