American politics is a logical choice of topic because of its relevance. The news is filled with events from local, state and federal governments, many of which affect you on a day-to-day basis. Make your paper current by taking one of these topics and refining a focus from it. For example, if the president delivered the State of the Union Address recently, use its content as a jumping-off point for your research by comparing it to the previous year's State of the Union, assessing whether its goals are realistic, or taking it in any other number of directions.
Government policy is a more specific topic, as it describes the principles governments use to turn ideals into realities. Investigate the various policies of American politics in relation to each other, or analyze the effectiveness of one. American government policies relate to healthcare, infrastructure, illegal drugs, immigration and other matters. When researching policy, for example, you could examine the processes through which aid money is delivered to third world countries, or how different governments' policies affect an industry such as healthcare.
Comparative politics is the comparison of different governments, policies or both. Use your term paper to draw comparisons and contrasts between two governments. For example, compare the U.S. healthcare system with that of another nation, and draw conclusions as to which country's policy is more efficient and financially sound. Alternatively, compare and contrast the structural foundations of different governments by researching electoral processes or the different parts of governments.
Political science has a number of theories, such as libertarianism, utopianism and pacifism. Write a term paper that investigates these theories, then compares them to the real world to see how well they have worked in practice. Your argument can focus on the soundness of the theory and on the soundness of its application. If, for example, libertarianism seems ineffective in an example you find, is this because libertarianism itself is flawed or because it is not applied effectively? These questions can be answered at length in term papers.