Coronavirus State and Local Financial Assistance Act This bill (1) directs the Department of the Treasury to establish a State and Local Government Coronavirus Relief Program under which Treasury shall make monthly grants to states to make up for revenue lost from March 1-December 31, 2020, due to COVID-19 (i.e., coronavirus disease 2019) and social distancing steps taken by the state and its political subdivisions, and (2) appropriates $500 billion to carry out the program. To be eligible to receive a grant, a state must (1) compile estimates for the revenue lost by the state and each political subdivision, and (2) submit an estimate to Treasury by the 20th of each month. Treasury shall make grant payments to a state within 15 days of receiving a loss estimate. The bill sets forth requirements with respect to pro rata distribution of funds, treatment of overpayments, and distribution to political subdivisions of a state.