I feel your question could use a bit of clarification. Which aspects of the Bewitched -> Sally the Witch -> Magical Girl genre do you seek to find similarity to?
E.g.: are you hoping to learn of other U.S. products (be they TV, music, books, pottery styles, ...) that were wildly popular in any other country and spawned local successors? Or specifically are you looking for anime/manga genres with this sort of origin? Specifically coming from the U.S., or anywhere? Specifically TV series, or anything?
Not exactly what you asked for but something similar in regards to Spaghetti Western Genre.
While it is really difficult to pin point origin of Spaghetti westerns, since Western movies were already being made in Europe with some of the characteristics of the movies that we later came to associate with the genre, A fistful of Dollars was the first movie that is decidedly Spaghetti Western and also very successful. A lot of movies after A fistful of dollars tried to copy and adapt elements from the movie.
A fistful of dollars is a remake, though unattributed at the time, of Akira Kurosawa's Yojimbo starring Toshiro Mifune. Yojimbo itself was Kurosawa's tribute to the broader Western genre with the lawless frontier far away from the reach of government. Unlike most of the Westerns it had a protagonist who was not entirely noble. There was a sequel to Yojimbo called Sanjuro but it is quite different from second installment of the man with no name trilogy starring Eastwood.
So not exactly the success of Yojimbo in US or Europe but a remake of Yojimbo led to origin of a new genre.
Another fun fact George Lucas was inspired to make Star Wars after watching Kurosawa's Hidden Fortress in which Mifune, who was part of almost every Kurosawa movies, plays a general trying to take his princess across enemy territory to a neutral Kingdom after they have lost the war. While not as clear cut as Yojimbo and A fistful of dollars, the similarities could be clearly seen not least in portrayal of the two robots.