Apparently less than 15-minutes of athletic action in a typical 3-hour game, with ~45-minutes devoted to advertising:
[2020] How Much American Football Is Even in an American Football Broadcast?
https://news.ycombinator.com/item?id=22218909
This explains why NFL RedZone exists.
Fun comparison, a typical Formula 1 Grand Prix clocks in at ~1.5 hours. Live race broadcasts (e.g. Sky Sports F1) will typically show the entire race with no commercial breaks or interruptions. Same goes for MotoGP (e.g. TNT Sports), where a sprint race (~10-12 laps) takes just 25 minutes, not including post race podium and interviews.
English Premier League game durations come in at just under 2-hours with a full hour of athletic action, the remaining 50% occupied by a 15-minutes halftime, substitutions, free kicks, and a mere 10-minutes of commercial interruptions.
Ever since my parents got a DVR, my dad switched to recording NFL games and then only starting to watch them until maybe an hour or so after the kickoff. He'd fast forward through the numerous commercial breaks (like before AND after each kickoff whenever someone scores? come on...) and eventually catch up near the end of the game.
Yeah, NFL games are kind of crazy. I missed a MNF game recently and saw it on YouTube the next evening (and somehow I hadn't spoiled the score for myself). It was less than 2 hours without a single play or comment edited out. Aired live, it was closer to 3:30. Literally 1/3 commercials. It's a little excessive.
If I get into a rhythm with the "advance ten-seconds" button between plays I can get down to around an hour, without missing any plays, or pre-snap action. It'd be a lot less, even, but there are times we want to see the replays, and other times I "miss" and have to jump back. It's amazing how much dead time there is in American football.
It's amazing how much non-action time there is an NFL broadcast. Some people don't watch because of it, but I suppose enough do.