Federal Emergency Management Advancement of Equity Act or the FEMA Equity Act This bill addresses equity in federal disaster assistance policies and programs. The Federal Emergency Management Agency (FEMA) must develop and implement a process to ensure equity in the provision of federal assistance and throughout all FEMA programs and policies. Additionally, FEMA must establish metrics to measure the efficacy of the process and seek input from relevant representatives of state, regional, local, and tribal governments; community-based organizations; subject matter experts; and individuals from underserved communities impacted by disasters. FEMA must designate a senior official as an equity advisor. The bill establishes in FEMA an Equity Enterprise Steering Group. The chief executive officer of an affected county may submit a request for a presidential declaration that a major disaster exists if (1) the governor of the state or territory in which the county is located does not request such a declaration, (2) the affected county is not included in a request for assistance made by such governor, or (3) the affected county communicates with that governor about the disaster or potential request for a major disaster declaration before the relevant period has lapsed. The Government Accountability Office shall issue a report describing the factors that FEMA considers when evaluating a request from a governor to declare that a major disaster or emergency exists and to authorize specified assistance.