Expanded SUTA Act of 2018 This bill amends the Rural Electrification Act of 1936 to expand the Department Agriculture (USDA) Substantially Underserved Trust Area (SUTA) authority to: (1) include all programs administered by the USDA rural development mission area, and (2) specify that USDA may use the authority for certain communities within former Indian reservations. (Under current law, the SUTA authority is limited to certain programs administered by the USDA Rural Utilities Service. The authority permits USDA to modify or waive certain requirements and procedures for loans and grants in order to improve the availability of programs in communities on trust land [e.g., land held in trust by the United States for Native Americans] that have a high need for the benefits of an eligible program.)