Block Iranian Access to U.S. Banks Act of 2020 This bill temporarily prohibits the Department of the Treasury from authorizing a U.S. financial institution to provide financial services, directly or indirectly, to Iran. The President may waive this prohibition after issuing a report that such financial services are (1) required solely for the provision of medicines, medical equipment, agricultural commodities or humanitarian assistance benefitting the people of Iran; or (2) not provided in connection with a foreign person that engages in sanctionable activities.