Logistically speaking basketball is a much easier game to play. There are hoops everywhere and if you got a ball your good. The NBA has a unique system where a easy to access sport was created and curated in the U.S. while soccer reigned supreme everywhere else. They had time to grow a sport that was easily adoptable for many people.
Football is much harder to just walk outside and play not to mention its just a shittier version of Rugby. The only survival of the NFL I see would be a slow movement towards a Rugby Football hybrid of some sort, no pads smaller teams, lots of speed and skill. With that being said I think we still have quite some time to go before the NFL really begins to fizzle.