Ole has actually hit the nub of the problem here. There are myriads of traditions, so which one(s) are we talking about here? Those of the British Isles? US Appalachian? US country blues? Cajun? Sami? Bhutan? Denmark?

Chuck Berry probably won't transfer to British Isles 'folk' repertoires, and, given time one or other of the 'traditions', because his songs are intrinsically american. On the other hand, his songs have already crossed over into the cajun repertoire and in the course of time will no doubt be regarded as 'traditional' cajun songs.