A 2008 academic study compared the level of public knowledge about current events in Denmark, Finland, England and the U.S. It found that the countries with TV/radio dominated by public broadcasting -- Denmark and Finland -- were the best informed. Our country, dominated by corporate media, was the least informed. The study's authors suggest that differing media systems play a role in those results.
In a related item: A 2003 study of U.S. public knowledge of facts related to the Iraq War found that misperceptions were greatest among those whose primary info source was Fox News, least among those whose primary info source was public broadcasting. (A Pew poll taken in Aug. 2010 found that almost 1 in 5 Americans believed President Obama to be a Muslim; only 34% knew he is a Christian. 43% chose "don't know.")