Miss Americana is a "Super-Girl" type who is powered by feelings of nostalgia and basic Americana. I thought that it was a neat concept that had never really been done before. She's also kind of a "legacy character," having inherited her powers and heroic persona from a family heirloom that once belonged to her great-grandmother, who was the original "Miss Americana." It is not explicitly stated where she or her great-grandmother are from originally, but since it is said that Teresa found the magical scarf in her attic where she lives in USA City, that can be taken to mean that her great-grandmother was a heroine local to the same city, and Teresa herself is a home-grown native of the area as well. And, perhaps, being a historian, she might have heard of the original "Miss Americana," but maybe she never knew that the heroine was one of her own blood relatives!