United States Semiquincentennial Commission Amendments Act of 2020 This bill modifies certain requirements of the U.S. Semiquincentennial Commission, which was established to provide for the commemoration of the 250th anniversary of the founding of the United States and related events. The bill modifies the membership requirements of the commission; changes the date by which the commission shall report to the President with its specific recommendations for the commemoration of the 250th anniversary and related events to March 31, 2020; and grants the commission the exclusive right to use, and to allow others to use, the official marks, imprimaturs, and logos of the commission.