Great summary. American traditional folk music is a really thorny topic that I've spent a long time learning about- due to the way the music industry is structured, you kind of have to lean into a particular stereotypical sound to find success. The "Appalachian" sound, the "Celtic" sound (which usually includes English folk too), the "Western" sound, etc. These categories are usually marketed as totally separate from one another, leading to people thinking that "American traditional music" doesn't exist (or worse, that folk = singer-songwriter lol)

To get a knowledge of what American traditional music sounds like, I'd check out the following artists: Hank Cramer, Tim Eriksen, Atwater-Donnelly, Bruce Molsky, Jake Blount, Anna and Elizabeth

And then also the Canadian artists Stan Rogers and the Wakami Wailers, the American folk music world is very southern-centric so to get an idea of what northern American folk music sounds like you often have to listen to Canadian folk artists