We had so many professional teams in the early 1900s based, obviously, on a huge influx of footie-enthused immigrants. It's a shame the US soccer federation didn't capitalize more on this, given that the Lamar Hunt Open cup is one of the oldest tournaments in the world, and there were several professional teams, some of which played exhibition games abroad in the 1920s. Seems like an opportunity missed. Collegiate soccer has been around since the 40s but youth soccer only since like the 70s or so...I suspect the latter is what makes us lag as the game was largely viewed as "niche" or a game for "foreigners" prior to this, and only since like the 70s did the game open up to a broader population due to youth leagues (which started to pay off some 20yrs later). It also didn't help that there was only one CONCACAF spot for the WC from 1954 up until 1982, and that spot invariable went to Mexico. This tended to likely kill any development at the National team level for a good while.
I think Wynalda is correct about the coaching development: the US doesn't do enough to develop good coaches...just look at what Iceland did in the early 2000s; they dumped tons of money into new fields and especially into coaching development. And they now punch way above their weight on a per capita basis.