Compare tv ratings for MLB to the NFL.
26% increase year-over-year TNF game....
https://sports.yahoo.com/ratings-bucs-patriots-thursday-night-football-stay-170933480.html
Football ratings are impacted by a lot of things - CTE is their biggest problem. If participation at the youth level declines, those aren't going to be watching as much. Two teams have relocated withing the past year - destination LA, where football isn't huge.
They'll lose a few views over the Anthem protests, but the impact will be marginal.