Fred, you are so right. There is no pure folk culture or unique national expression because there are always elements from predecessors or other parts of the world.

Cecil Sharp was hunting English Folk Song in the Appalachians in the US because he thought that this was the isolated carry over from early times which he considered not
to be extant in his time in England. Hence, the search which in my view culminated in a American musical expression. Of course, Sharp thought that the five-string banjo was a bowdlerization of the "English" folk song (I guess in the way that some would consider the electric guitar as such for any acoustic folk song.)

Understanding the roots of any given culture leads to antecedents that influence it.
Music from Galicia, Spain on Irish piping or traditional music might be
a case in point. (The Celts got around).

So if there is no pure race, nationality or culture, this then begs the question as to what defines a culture that excludes everything else not part of it.

Folk Against Fascism can show that the roots of English music run deep as a river flowing from other tributaries. This has little to do with a mythologized identity based on xenophobia.

When visiting St. Anne's College in Cape Breton, we talked to Mrs. Jones who really studied Scottish music and culture. Here's where they teach piping, dancing, fiddling etc.
Her statement was quite clear. "The Scots are the biggest mutts in the world."

Frank Hamilton