MSN.COM has sample questions from the United States citizenship test. one of the requirements to become a United States citizen is that foreign-born people must pass the citizenship test. MSN did admit to selecting the hardest questions from a 100 question sample. There are quiz questions about historical documents, events, and people in United States. You are also aksed facts concerning the government and current people in government.
Kids that are taking United States history or American government will probably do better than their parents that have been out of school for years. Maybe this is something that you and your kids could try and then compare results.
You can take the citizenship quiz here. You can try it as see how well you can do.
I was not to proud of my quiz results. I thought that I would have done a lot better.