That was something like 80 years after the invention of the dixie cup though, so I doubt that TV show would have helped anybody in America struggling with expla

That was something like 80 years after the invention of the dixie cup though, so I doubt that TV show would have helped anybody in America struggling with explaining the name Llywelyn to other Americans in the late 19th or early 20th centuries. The assumption that Americans anglicized their names did so by accident because they were illiterate is just silly. I'm sure that happened sometimes, but loads of people anglicized their names deliberately in an attempt to conform with local expectations. One of my great-great-grandfathers, a literate German speaking immigrant to America, changed his name from Müller to Miller. Why? Well I can't ask him, but probably because it was the thing to do. This sort of thing was very common particularly during that time period. The later means the same thing, sounds about the same, but crucially would be more familiar to anglophone Americans. And Müller is comparably easy. (To be clear, my last name is not Miller; I have an non-anglicized but reasonably common Italian surname.)