~snip~
A lot of people claim that association football is not very popular in the United States, because the MLS is nowhere near NBA or NFL in terms of revenues. But it may also be due to the fact that the quality of MLS may be low. I don't know how much was the viewership for the recently concluded 2022 FIFA World Cup in the United States. I would assume that it was quite decent, since a large part of the American population is of migrant descent, and originates from football crazy nations such as Mexico, Colombia and Venezuela.
The thing is that the US has a lot of very popular sports, as you mentioned, like the NBA, NHL, etc.
But in South America and Europe, basically there is no rival to football. Any other sport is a low second.
In those continents, when there's an important football match, the whole country stops. Everyone is either at the stadium, or watching it on TV at home or at a pub.
And when their home country scores, you can hear the roar from everywhere.
That experience is not seen anywhere else in the world other than South America and Europe.