Thanks for the comments.
I have to agree that there must be significant interest Brevets in the Northeast. And of course, as others have mentioned there are "other" 1200k rides sprinkled about North America.
I have less interest in Brevet riding simply because the particular "metric distances" mean less to me than the concept of the "double-century". Obviously the UMCA engages the most talented riders but many of their main competitions are non-drafting "solo" format and some rides require support staff and vehicles.
I think I need to study "ultra-running" associations and competitions. Maybe I can find some parallels that could be applied to Long-Distance riding and come up with an event-style and format that would be attractive to all types of extreme athletes, whether their forte be swimming, triathloning, ultrarunning etc.
I just feel that the nature of long-distance cycling organizations is currently skewed in a manner that limits cyclist's potential interest in longer-distance, single-day group rides..