I don’t doubt what the German coaches would say but I would suggest that the “clubs” are not all or necessarily what North American track aficionados may think of as “club”. I am referring particularly to clubs like Bayer Leverkusen that have/are track and field clubs but in that example anyway they are not the “main” sport but the club as a whole is huge with lots of money involved as in Bayer and Adidas (tsvbayer04.de).
I still believe the two controls are China = huge population base, just percentages…and Germany (or for that matter I suspect most European countries) = track and field is “known” year round for a larger portion of the general population [there have been a few threads about making the sport better but IMO it will always be tough if it only happens in the eyes of the general populous every 4 years; unless I am completely mistaken the health culture is just different than in North America in both places as well].