Flow, I am too young to have known Peter Snell from High School days. But I taught at Mt Albert Grammar in the early/mid 80's and there was still a few 'old' guys who were teaching there then who knew and taught Peter when he was there.
I used to look after all the "Records" for School Athletics and Mike Macky was the School record holder for 800m (Still is !!) at 1:57.8. Snell had a crack at it but came up short.\
The record has to be set on "Athletics Sports Day "
As for your other questions.
Without any evidence I would say that w have always had a "distance running" culture in NZ.Harrier Clubs up until recent years were strong "Social groups" that met on a regular basis with the guys training together. Arthur was critical in the ideas of training , particularly in the 50's, 60's and 70's.
But Hey ! You work with the likes of Russ Hoggard, he would have some ideas about why our Distance runners have been so successful. He has been around forever and seen the "us and downs" of NZ Athletics.
To go back to the Harrier clubs. In july I went down to Wellington for a visit and in the process had a run with the Scottish Harrer Club. My estimate that day would be about 100 runners (Foul day too !!). The groups out running contained everything from National reps to over the "over 60's". I ran with that group (as one of the youngsters) and we were out the longest of any group that day and would have covered 10 miles on Wellingtons rugged hills.
How many NZ Harrier Clubs would have done a similar thing that day ???. Probably Dozens.
How many in the US ?? Probably Zero !!!!!
I guess you could say it is a cultural thing !!!
As for the Bowerman question. I feel (this is totally personal) that Bowereman saw the Lydiard success in 1960 and decided to "get some of that Knowledge" and came out here and not only picked up the knowledge but made a good friend. Being somewhat of an entrepeneur he saw he could "sell" jogging to the general public and took those ideas to the US and published a book about it.
I never met Bowereman but I wonder if the 2 guys were not disimilar in their personalities.
Whew ! I must get off to School !!!!