I think part of the answer lies in the cultural make-up of the first 13 colonies. Each was settled by immigrants from a specific area of Europe, and each retained strong ties to its cultural homeland back over the seas. There was no "United States" before the Revolutionary War. Rather, there were independent colonies, each with a somewhat different heritage based on its early settlers. Each preferred its own styles, its own cultural values and to some extent governing forms, etc. And they kept in relatively close contact with their "home" country in Europe. Until the rumblings of the Revolutionary War pulled them together in common cause, the individual colonies were not closely associated with each other, as they had to be to survive the war. New York preferred Dutch products, Pennsylvania preferred Germanic products, Virginia preferred British products, etc.
Strongly Germanic areas used Germanic locks, while areas settled by British immigrants preferred British style locks. As we've all read, for several generations labor was scarce in America compared to Europe where it was much more plentiful, so quality locks could be made in Europe and exported to America for substantially less than if they were made over here. Of course, if an early Amerian gunsmith didn't have an imported lock available, he could generally make one, but it cost the new owner more.
Germanic locks were imported into the Amerian colonies, and used primarily where German immigrants had settled. Kauffman in his "The Pennsylvania-Kentucky Rifle" discussed early locks used in Pennsylvania, including records of Germanic locks being imported by major hardware dealers. Kauffman also provides data on the growing number of lock makers in the United States by the turn of the century, i.e. 1800, and later. So it would seem that up to about 1800 there were some cultural demands for retaining the use of certain type locks that early settlers were "comfortable" with, but after about 1800 (not an exact time, but around that time) as locks began to develop oval tails and goose neck cocks, it appears that the British influences began to win out in a wider area, beyond just the initial British settled areas. Shelby Gallien