Western Wildfire Support Act of 2021 This bill establishes activities to address wildfires. The bill requires the Department of Agriculture (USDA) and the Department of the Interior to establish spatial fire management plans before the end of FY2024. The bill establishes accounts in the Treasury for addressing wildfires, a program to train and certify citizens who wish to be able to volunteer to assist USDA or Interior during a wildland fire incident, a program to award grants to eligible states or units of local government to acquire slip-on tank and pump units for a surge capacity of resources for fire suppression, the Theodore Roosevelt Genius Prize for the management of wildfire-related invasive species, and the Management of Wildfire-Related Invasive Species Technology Advisory Board. The bill also requires the Department of Defense (DOD) to reimburse a state or federal agency for the costs of wildfire suppression as a result of a fire caused by DOD activity, requires the Joint Fire Science Program to work with unmanned aircraft test ranges to carry out research and development of unmanned aircraft system fire applications, requires federal and state disaster preparedness programs to include postdisaster assistance, and authorizes the Federal Emergency Management Agency to provide funding to a state agency to establish and operate a website to provide information relating to postfire recovery funding and resources to a community or an individual impacted by a wildland fire.