Street ball is important, but don't underestimate the top-down effect that having millions of dollars invested at all levels of the game creates.
Those kids might play street ball, but they are discovered, developed and progress through an incredibly sophisticated and efficient (and of course, sleazy and underhanded) network of scouts, agents, parents, AAU coaches, junior high and HS coaches and college coaches, all of whom are underwritten by boosters and shoe company money.
By comparison, the soccer development network is strung together with bailing wire and bubble gum. I'm sure if you go back four years you'll see me making this same point, but we're the only country in the world that requires that our best soccer athletes subsidize their own development. MLS academies are starting to gain a foothold, but they're still miles behind the travel clubs that constitute the bulk of the development system.
Even more insidiously, the travel clubs need to win to attract kids and satisfy the parents writing the checks. This means our U12-U16 kids are learning exactly the wrong way: specializing too early, playing (in the literal sense) too little and being driven to achieve results rather than developing their individual skills. The result? Players who work their ass off for the team, who can get a result but who ultimately pale in comparison to the soccer elite because they lack the technique of world class players.
2 15 year-old boys. One great at hoops, the other soccer. The basketball player will be recruited by an AAU coach, a HS coach and possibly street agents, all of whom will be giving him opportunities to play at progressively higher levels of the game at little or no cost to him and his family (and possibly even enriching it) .
The soccer playing kid might get lucky and get swooped up by an MLS academy, but the odds are against that. He'll need to be playing for one of the regional mega-travel clubs. He will need to find someone to pay many thousands of dollars for him to get access to the best competition and instruction, and that instruction will be the complete inverse of the AAU model.
The USSF has been aware of this for a long time. Their publications on youth development expressly try to stop this sort of problem, but they fall on deaf ears. Most of the travel teams in these parts have boys as young as 10 already specializing on the field, and if a travel club gets poor results over a season the horrible helicopter parents will drop it in a heartbeat for a hot, new option that wins games.
So what I'm saying is that street ball is nice, but there is a systemic problem that's even bigger than that. Look again at that Belgium piece I linked to a while back. Now that's a tiny, tiny country, making it so much easier, but they understood that to change the soccer culture of a nation and produce an elite national team you have to change the way players are recruited and taught. We're a much larger and diverse nation, but that doesn't change the fact that our national soccer DNA relies on the same thing.
Edit: Realized I didn't even get into what a cancer the NCAA is when it comes to soccer, but it's late...
