Based on fans that follow the sport, not those that compete/play it.
pro football, pro baseball, nba, college basketball, college football, then who knows...we used to watch tons of WWF
NASCAR
1. Football
2. Baseball
3. Basketball
4. Hockey
5. Soccer
6. Boxing
7. Auto Racing
8. Golf
9. Tennis
10. Mixed Martial Arts
https://sport.one/the-top-10-most-popular-sports-in-america/