Wildfire Defense Act This bill directs the Federal Emergency Management Agency (FEMA) to establish a community wildfire defense grant program and requires other actions by FEMA, the Government Accountability Office (GAO), and the Forest Service with respect to wildfires. In awarding grants, FEMA must give priority to state and local governments, Indian tribes, and joint authorities that will carry out projects or plans supporting a low-income community in a fire-hazard area or a severe disaster impacted community in a fire-hazard area. The GAO shall publish (1) a report on authorities and programs that are available to protect communities from wildfires; and (2) a study on the potential for a community wildfire defense plan to qualify for a certification identifying a level of wildfire survivability and resilience, and how to incentivize insurance companies to accept the certification. The Forest Service shall develop and publish a map depicting at-risk communities. FEMA shall prepare a report relating to insufficient radio frequencies, barriers to interoperability of radio frequencies, and available products and technologies for overcoming barriers to interoperability for wildland fire management.