Modern Television Act of 2021 This bill establishes measures to prevent blackouts of television broadcast stations, including requiring good-faith negotiations in broadcast agreements and providing for outside arbitration of certain negotiation disputes. Specifically, the bill requires a station and a cable or satellite service to negotiate in good faith when attempting to reach a marketplace agreement, and it requires the cable or satellite service to retransmit the signal of a station for up to 60 days while the parties renegotiate an expired agreement. The Federal Communications Commission may require a station and a cable or satellite service to submit to binding arbitration to resolve any dispute that may arise (the parties must be retroactively paid for content aired during this time). Further, a station is prohibited from requiring payment from a cable or satellite service for customers of the cable or satellite service who do not receive the signals of the station from that service. Additionally, the bill repeals specified provisions, including those related to retransmission consent and compulsory copyright licenses. The bill also disallows federal, state, and local authorities from regulating the rates of a cable or satellite service. The Government Accountability Office must assess the impact of the bill.