I think Tony Kornheiser (sp) said it best. In the USA , our sports plate is full. Each month a major sport dominates the sports narrative. There is simply no room for soccer in the US as a major sport. At best for the forseeable future the highest they can achieve will be 5th
I'm not sure why sports like soccer and the WNBA can't just be happy with whatever attention they get. I'm nearly 60 years old, when I was young, back then they said soccer was going to be the next big thing. It's not. It never will be in America. Yes, most high schools have soccer now, something that wasn't around 40 years ago. But it was added mainly for bigger school to increase extracurricular activity opportunities, like tennis, golf, wrestling, etc.
I'd say in certain pockets of the country, more in major cities. Organically, across the entire United States, it's football / basketball. Baseball sadly has fallen off, and maybe that's where soccer has made some in roads. But alot like baseball, people / kids play baseball, but not many watch unless it's the big league level and in major baseball markets. But as I said, this was talked about 50 years ago like it was going to take over by the 80's and 90's and we're still waiting. Now globally, yes, I get you for that. But I think the original post was to the interest level in the states.MLS may be on a similar level to the WNBA within mainstream sports media right now, but international soccer is leaps and bounds ahead of the WNBA in terms of popularity.
Every major city in the US has a growing fan scene and many kids in these cities are opting to stick with soccer as their main sport as they grow up - especially over football and baseball. I see it on a first-hand basis every day.