Even though I'm not American, I took the test at dontvote.org. (The idea is that if you don't know who you're voting for, you shouldn't vote. I would perhaps change the "don't vote" to "find out!", but meh.) I scored 49.71%, getting an "F". (I should apparently consider moving to France. ;)
So consider this a baseline. If you take this test and are American, if you get less than 50% then you're dumber than a stupid Brit who doesn't even live there. ;)