American Security Drone Act of 2021 This bill bans the procurement or use by the federal government of unmanned aircraft systems (UAS) that are manufactured or assembled by certain entities, including entities subject to influence or control by China, with exceptions. The ban includes associated elements that are required for the operator to operate safely and efficiently in the national airspace system. The Department of Homeland Security, the Department of Defense, and the Department of Justice are exempt from the restriction under specified circumstances. The bill sets forth further exemptions regarding the Federal Aviation Administration, the National Transportation Safety Board, and the National Oceanic Atmospheric Administration. Federal funds may not be used to procure certain UAS from a foreign entity, with exceptions. All executive agencies must account for existing inventories of UAS manufactured or assembled by a foreign entity in their personal property accounting systems. Inventory data related to UAS manufactured or assembled by a foreign entity may be tracked at a classified level. The Federal Acquisition Regulatory Council shall prescribe regulations or guidance to implement this bill's requirements pertaining to federal contracts. Government-issued purchase cards may not be used to procure any UAS from a foreign entity. The Office of Management and Budget shall (1) establish a government-wide policy for the procurement of UAS, taking into account information security; and (2) contract with a federally funded research and development center to study certain UAS-related issues.