this is a valuable discussion and there might be a book in it.
After the intial cadre of builders returned from Europe in the mid 70s, the craft spread out to a larger group of builders, mostly clustered at the coasts
Also the influence of Masi CA, and Mario Confente's "giant leap" in terms of elevating the level of craftsmanship and attention to detail is worth noting
As is the work of Tom Ritchey who had some innovative design ideas, including fillet brazing
Builders of this period really raised the bar and established the US as a center of expertise in framebuilding.
/markp