Sports bars pay special fees to be able to show sports games. A restaurant would have to pay hefty fees to each league they broadcast within their building. To play an NFL game on their TV, they’d have to pay the Nation Football League a fee.
One exception is from section 110 of the copyright law: you can show the game to a big crowd, provided you’re not charging a fee for people to watch it and that when you tune in, you’re only using a single receiving apparatus of a kind commonly used in private homes.
Cable companies apparently periodically have done legal crackdowns on bars that subscribe to cable TV under a residential contract for display for patrons. The TV must be less than 55 inches to be shown at private parties.
There are actual auditors who go around and check how many people attend a bar for a game, because the special fees for broadcasting a game are partly calculated by how many will be attending.