I honestly doubt Americans on average are any more or less ignorant to the rest of the world than people from pretty much any other country. Of course the most ridiculous of people are going to be put on youtube and have the limelight. I'm sure a similar percentage of the populations of most other countries are just as ignorant. Reason America is targeted most for this is because America is considered one of the most powerful countries in the world, so it is naturally going to get the most criticism and hatred towards it.
I don't have any facts to back all this up, it is just simple common sense, and my opinion.