Safe Line Speeds During COVID-19 Act of 2020 This bill directs the Food Safety and Inspection Service of the Department of Agriculture (USDA) to temporarily suspend any waivers and not issue new waivers related to line speeds in meat and poultry establishments and inspection staffing requirements for such establishments through 90 days after the date on which the COVID-19 (i.e., coronavirus disease 2019) emergency period is lifted. Additionally, the implementation of, and conversion to, the New Swine Slaughter Inspection System must be suspended. No funds made available to USDA during such period shall be used to develop, propose, finalize, issue, amend, or implement any policy, regulation, directive, constituent update, or any other agency program that would increase line speeds at meat and poultry establishments. Not later than 90 days after the end of the period, the Government Accountability Office shall conduct a review of actions taken by specific federal agencies, including USDA, in response to the COVID-19 pandemic to determine the effectiveness of such actions in protecting animal, food, and worker safety.