I think what Burnsy points out is worth noting: there never were a couple 2:07 guys around and several more within a few minutes at a given time in the US. Compared to today's fairly routine international times, we never did have many - just occasional outliers (thankfully, there is sometimes one US guy to root for).
What I really wanted to write was that I was impressed that many of you - including Ritz himself - see it like I do: the whole HS/NCAA thing (and significant peer/parental/societal pressures) discourage any real long-distance training and racing until approaching the end of one's prime. The court of public opinion expressly forbids non-school-affiliated running if you have eligibility. If you trained through most school-related races with an eye toward the marathon then immediately moved to roads afterward then maybe it would work, but how many times did the NYC commentators comment on so-and-so's young age yesterday? Your teens are 'supposed' to be spent earning the scholarship. That ain't happening if you're on the roads. Then you're stuck at the shorter events for another several years. Contrast that with a training group in Iten in which college is a concern of no one but winning Berlin certainly is a priority. Many will try and some will truly succeed. Here, no 20-year-olds are even trying. That pretty much guarantees that none will make it by 25.
Just my opinion. Forgetting about your High School's team and coach is a start, but that ain't happening anytime soon in this country.