When did popularity of boxing decline in US?

Didn't Ali give the sport a shot in the arm when he came on the scene though? His 70s mega fights had hundreds of millions of worldwide audiences.

 

Yes, he was often credited with reviving boxing early in his career when he campaigned as Cassius Clay. His childlike "poetry" and his ability to predict the round in which his foe would fall gave the sport a big publicity and energy boost.
But after he won the title and announced his allegiance to the Natuon of Islam he was seen as hurting boxing. Those were the angry Ali years, and he did boxing no favors.

 

Mid 2000s I'd say. The US never had a mid 2010s revival that sparked massive domestic interest like the UK (Froch - Groves 2, AJ - Wlad etc) or Japan (Yamanaka, Hasegawa, Inoue's debut etc). Once Mayweather retired it's been on a slow decline.

I've noticed that boxing seems to do much better overall nowadays in countries with more nationalised and concentrated fanbases

 

I would say taking all those punches couldn't have helped even if it may not have been the cause. He should have probably retired like 5 years earlier.

 

They were both well past prime. Like not even close. For years AJ/Fury/Wilder all avoided each other. Got a Fury v Wilded fight but by then he was already old and he was clearly not the Bette between him and AJ