Long Bridge Act of 2020 This bill authorizes the National Park Service (NPS) to convey to Virginia or the District of Columbia any federal land or interest in federal land under the jurisdiction of the NPS that is identified by Virginia or the District as necessary for the Long Bridge Project, a project to expand commuter and regional passenger rail service and provide bicycle and pedestrian access crossings over the Potomac River. The NPS may allow the temporary use of any federal land under the jurisdiction of the NPS that is identified by Virginia or the District as necessary for the construction of the Long Bridge Project.