I was born in Florida, spend a lot of time there, and have nothing against the state, but there is good reason to say that Florida has underperformed relative to its population as a boys high school distance running state. That is not the same thing as saying that Florida "cant produce quality runners-" simply that it does not do so at the same rate as some other areas of the country. The same is true for the South as a whole- it's the biggest Footlocker region by population by a good margin, yet it is consistently the weakest region. If I recall correctly, before last year, the South had never placed higher than 3rd in the team competition!
A lot of the perception of Florida not being a good running state is historical- Though it's the 4th most populous state, Florida had no boys place in the top 10 at Footlocker between 1992-2008! The good news is that Florida and the South do seem to have been improving in the past few years, and its to be expected that their national reputation hasn't kept pace with that. Based on what you said however, I would caution that Florida almost certainly would not have had 3 top ten guys at footlocker in the past 2 years if NXN did not exist. Pickering and Mizereck would have been bumped out of the top ten, and Clark probably would have as well- Tony Smoragiewicz was 9th at NXN and 3rd at Footlocker. Verzbicas was the only one of the guys who beat him at NXN who ran Footlocker, and there's a good chance that Rosa and/or Gedyon wouldn't have bombed at Footlocker.
I've seen people talk about the reasons for Florida's relative weakness, and the consensus is that it's mostly how huge football is, and how hot the summers are.