It is widely known that the UK produced some amazing local song and I will add seasonal celebration customs. Some borrowing has been documented but it is generally marginal to the individual local tradition. When I was in Durham in the 70s at University I found that a surprising number of people knew a good number of their regional songs and I heard them in the pubs. In the USA scarecly anyone knows the lyrics to a song and especially no one knows local folk songs. Nobody.

Must be less than 50% but hard to put a figure on it. But, it is easy to know when a song writer performer considers folk to be entirely contemporary.

Conrad
Conrad