It would help to know what sort of topic you are supposed to be writing about as there are so many aspects to American government. I will offer you three articles that I have read recently that I find very interesting.
First, there is this article which claims that American society is being split into an upper class and a lower class. These two classes are said to have very little in common. You might try to talk about whether this divide truly exists and (if it does) what impact it could have on the US political system.
Second, there is this article arguing that our government does not do things that will help people who are trying hard but who lack the skills or education needed to really prosper in our economy. You might try to explain why this happens and what might happen if this continues.
Finally, there is this article claiming to explain why it is so rare for us to get really good candidates for president. You might use it to talk about what sort of abilities a good president needs. Or you could talk about whether there is something wrong with our system that makes it hard for good presidents to get elected.
It can be any topic related to to U.S. Government and Politics. I must be able to explain the relationship it has to to relevant political science concepts and/or U.S. Government concepts.