It's because FIFA is being held accountable, as it literally involves every country on Earth.
North American sports leagues are accountable to no one. Especially not from governments like FIFA. A) a significant majority of sports team owners are involved in politics. They bankroll one of the two parties, aka oligarchs. B) I'm not familiar with any North American sports leagues other than the NHL. But like the NHL it is used by the government as a propaganda tool aka jingoism as required military nights and players must wear military style jerseys + many NHL games start like a third world military parade.
Another thing is lack of free press. It is hard to take leagues seriously where there is no legitimate independent anti-doping control. It does not follow the WADA code and does not allow USADA or WADA to test. I have yet to see an NHL journalist criticising the NHL's anti-doping efforts. Probably because that person would immediately lose his/her accreditation.
Like for example there's the case of Boogaard, he even failed the lame NHL doping test several times, nothing happened. NHL team doctors gave him extremely strong painkillers like they were candy. If this happened in Europe then many people would have gone to prison for many years. NHL has quite a lot of skeletons in the closet; deaths, suicides, brain injuries, addictions... But you don't see any 'journalist' holding the NHL accountable. Everyone's like, let's move on there's nothing to see here.