I admit to having a bias toward the social sciences--I was a history major after all. I find the result upsetting. I did a little digging around to see what could be curdling the results for so many of the roughly 200,000 individuals who take the test each year. Again, I am always impressed with the amount of information that the College Board provides. I poked around a little and found sample tests and review guides and a highly informative guide to the test. The test covers six general areas with the preponderance dedicated to the institutions of the national government; two major sections are devoted to the institutions: "Institutions of national government" and "Constitutional basis for federal government." Other areas are "Political beliefs and behavior," "Organizations for public influence," "Civil rights and civil liberties," and "Public policy." Seems pretty straight forward but as I looked over the sample questions it came back to me how daunting dual federalism and the establishment clause were to me when I took Civics those many years ago.
I suppose my second bias is that I love our American Government materials. Take a look at Jerry Rosenberg talk about federalism or Matthew Dickinson discuss voter behavior. I think you will love it too.