Rebuilding Rural Roads Act This bill modifies the definition of rural area that is used for the Rural Surface Transportation Grant Program. For the purposes of the program, the bill defines rural area as an area outside an urbanized area that has a population of over 20,000. (Current law requires a rural area to be outside of an urbanized area with a population of over 200,000.) The grant program supports projects that improve and expand the surface transportation infrastructure in rural areas to increase connectivity, improve the safety and reliability of the movement of people and freight, generate regional economic growth, and improve quality of life. Eligible applicants for the grant program include states, regional transportation planning organizations, local governments, and tribal governments.