I agree with you on how boxing is bigger globally. But it is actually a fringe sport in the USA.
I attend a very large Uni in the United States as a European international student and nobody in my school know who Wladimir is.
Nobody. I asked so many about boxing and they admit they do know Tyson and to a extent Mayweather-Pac, but nobody know the heavyweights any more. (not in the states).
Even in the UK, very few people are interested in the Heavyweights from Eastern Europe. Now the good thing is the UK Heavyweight scene has been promoted a lot lately so that might change.
But the HW Division for sure is a dead sport in the United States. Why the hell will HBO reject Wladimir and why the HELL will Wlad fight in Germany now? It's because the Heavyweights flopped in the States.