Jacob Shelly at the Congressional Research Service:
Unlike the practice of some states that allow the Governor to postpone an election during emergencies, neither the Constitution nor Congress provides any similar power to the President or other federal officials to change this date outside of Congress’s regular legislative process. Congress has enacted more than 100 statutes identifying special powers that the President may exercise during a national emergency, but none include the power to postpone or cancel any state’s chosen method of appointing presidential Electors. During previous episodes of war, pandemic, or other deadly crises in American history, the presidential election date has never been changed in response to an emergency.