USACE Military Personnel Augmentation Act of 2021 This bill expands the types of Army personnel entitled to receive certain pay and allowances while assigned to the U.S. Army Corps of Engineers on nonmilitary public works projects. Currently, regular Corps officers and reserve Army officers assigned to the Corps are entitled to receive pay and allowances from funds appropriated for the project that they are working on. The bill entitles warrant officers and enlisted members of the Army, whether regular or reserve, to receive such pay and allowances when assigned to the Corps.