FEMA Assistance Relief Act of 2020 This bill modifies the federal cost share of certain emergency assistance relating to COVID-19 (i.e., coronavirus disease 2019). Specifically, the bill provides for (1) a 100% federal cost share of assistance provided under the emergency declaration issued by the President on March 13, 2020, relating to COVID-19 and any subsequent major disaster declaration that supersedes it; and (2) at least a 90% federal cost share of assistance provided for any emergency or major disaster declared by the President from January 1-December 31, 2020. These provisions shall apply to funds appropriated on or after this bill's enactment. With respect to the emergency declaration issued on March 13, 2020, the President may provide assistance for activities, costs, and purchases of states, Indian tribal governments, or local governments, including, among other things backfill costs for first responders and other essential employees who are ill or quarantined; increased operating costs for essential government services due to such emergency; personal protective equipment and other critical supplies and services for first responders; and costs of procuring and distributing food to individuals affected by the pandemic. The bill (1) directs the President to provide financial assistance to meet disaster-related funeral expenses (subject to the availability of appropriations), and (2) authorizes specified assistance in advance. FEMA must enter into an agreement with the National Academy of Sciences to convene a committee of experts to study the use of certain assistance to respond to an emergency that does not cause physical damages. The bill extends by one year federal disaster assistance to individuals and households.