You may want to explore several topics and then check in with your professor.
The library has access to many subject-specialized reference sources that would assist in this initial step, such as reference sources about American history, Public Policy, Health Care Policy, Supreme Court history, political parties, social movements, U.S.government and more.
A general encyclopedia will contain information about a wide range of topics.
The articles are:
A subject encyclopedia will be more focused and detailed information on a specific subject.
The articles are:
In-depth, non-biased coverage of the most important and controversial issues of the day, with regular reports on topics in health, international affairs, education, the environment, technology, and the U.S. economy.
The Congressional Research Service (CRS) - "The Congressional Research Service (CRS) works exclusively for the United States Congress, providing policy and legal analysis to committees and Members of both the House and Senate, regardless of party affiliation. As a legislative branch agency within the Library of Congress, CRS has been a valued and respected resource on Capitol Hill for more than a century." -CRS
As of 2018 CRS publications are now provided to the public by the CRS. Previously the publications were only available through your Congressional Representative or through various repositories that gather them such as the University of Tennessee's collection here - Congressional Research Service.
Note: To see an index of topics, from the main CRS site, leave the search box blank and hit the search button.