American soccer doesn't lack size or athletes, it lacks skill. I don't think the pay to play model is great, but I'm not convinced it's entirely reponsible for the lack of skill development. The same pay to play exists in baseball and hockey too, yet we consistently produce world class talent in both sports.
IMO, the bigger issue is the coaching base and the knowledge gap among parents.
I can drive to my small town's local baseball field and find half a dozen volunteer coaches who played college baseball, or at least high school at a high level. The same is true in football. Soccer isn't like that. My son played for a local travel program for a couple of years, and I think we had one coach in the entire organization who had played college soccer. Most of the coaches hadn't even played in high school. I'm sure that's different at elite clubs, but at the community level there simply isn't the same level of experience.
I coached my son's team almost by default because there was only one other parent who had played competitive soccer at any level. Most of the parents had virtually no understanding of the game, and I don't think that's unusual, even on a lot of high level travel teams..
Huge problem with the parents bc technical skills that separate elite players are developed almost entirely outside organized practice.
I can use baseball better to illustrate my point - if you see an 7 or 8 year old kid consistently barreling baseballs all over the field, that swing wasn't built during his team's two hours of practice each week. It was built b/c a parent knew what they were doing and spent countless hours throwing to him, working with him and getting the kid thousands of swings. Even the best youth coach, on a high level travel team, simply doesn't have enough time to provide every kid with that kind of individualized instruction and repetition.
Soccer is exactly the same. The difference is that instead of building a swing, you're building touch. A youth coach simply doesn't have enough time to give every player the tens of thousands of quality touches needed to develop elite ball control, first touch, balance, and creativity. That work has to happen at home, but we simply don't have enough parents who understand the game well enough to know how those skills are actually developed.
I saw the difference firsthand growing up. My parents were immigrants, and I played with a bunch of foul-mouthed eastern euro immigrant kids. The answer to just about every soccer problem was the same - Go juggle dammit.
We dominated kids who were bigger, faster and stronger b/c we could control the ball.
On top of that, American kids have endless entertainment options. It's not exactly common to see kids spending hours every day workign on any skill much less juggling a soccer ball. Culturally, we prefer activities that provide instant gratification, and improving your touch is about the opposite of that. It's repetitive, frustrating, and boring as hell.
Compare that to baseball. Squaring up a baseball feels good immediately. You see the ball jump off the bat and get instant feedback that you're improving. I'm not suggesting hitting a baseball is easy - it takes thousands of reps - but the process itself is simply more rewarding for most kids and parents.
Football requires even less technical development early on. A kid who's bigger, faster, and stronger than everyone else can dominate from Pop Warner through high school without spending much time developing technical skills. Soccer doesn't work that way - you have to be incredibly skilled with your feet to be a world class player.
Just one asshole's opinion.