Choose an issue that is best resolved by the federal government (or a national policy) and one that is best left to the states or localities. Make an argument about the current division of labor between the federal government and state governments. Should there be more regulation or less, and by whom? Be sure to use arguments and evidence to support your claims rather than simply stating your preference (or opinion). Remember to avoid the 1st person.
Some examples of issues: “Sanctuary Cities,” education policy (“Charter Schools” or “Common Core”), Obamacare (ACA), Same-sex marriage, Immigration policy (remember that Alabama and Arizona passed their own laws regarding immigration enforcement that were overturned by the Supreme Court during the Obama Administration, suggesting the federal government had precedence, only to have federal courts stay the implementation of the more recent Trump Administration’s travel ban), Legalization of Marijuana, etc.