Here's are a couple of reasons in my humble opinion why soccer still hasn't had the appeal in America. (Short version spoiler; we're wired differently).
PERSPECTIVE: National identities
Soccer is a national sport for numerous countries - one of the things potential fans dislike is the tendency for its players to 'writhe in pain' on the ground when bumped into.
Football is the national sport of one country, 'Merica (And you know that!) - one of the things fans love is, it is a sport that 'brings the pain,' and celebrates over it!
HISTORY: "But women have success and are popular every four years"
Well see, that's because of Title IX - so, they should be waxing the world. The world's best men's teams come from countries that not only don't have Title IX or any similar opportunities, but some take a dim view on women athletes period.
Also, its cost effective to start a sport with rolling out a soccer ball and a couple of gill-nets on a post.
My little NAIA college in 1972 started with four female intramural sports that grew into (The very next year) KCAC league teams. Those girls granddaughters or great granddaughters grew up and are playing soccer now, we should beat Japan.
Yes, the girls had a couple bumps in the road with Germany and Japan, but one invented the Blitzkrieg, and the other the Bushido Code. Still in the end, Merica babes will continue to dominate.