United States Anti-Doping Agency Reauthorization Act of 2021 This bill authorizes appropriations for the U.S. Anti-Doping Agency (USADA) through FY2030. The bill adds requirements that USADA be responsible for certifying in advance any testing conducted by international organizations under the World Anti-Doping Code for international amateur athletes and athletic competitions occurring within the jurisdiction of the United States; and promote a positive youth sport experience by using a portion of its funding to provide educational materials on sportsmanship, character building, and healthy performance for those participating in youth sports. The bill requires any action taken by USADA to enforce a policy, procedure, or requirement against a person with respect to a violation of federal law, including an investigation, disciplinary action, sanction, or any other administrative action, to be carried out in a manner that provides due process protection. The Department of Justice, the Department of Homeland Security, and the Food and Drug Administration must provide to USADA information relating to the prevention of the use of performance-enhancing drugs or the prohibition of performance-enhancing methods.