In all fairness, (is that an Irish idiom?) I don't think the Clancys, the Dubliners, or any of the Irish ballad groups that became popular abroad claimed all the songs on their repertoire were Irish. I'm sure if they introduced the songs they would have mentioned their provenance. It is not their fault if people assumed that the songs they sang were all "Irish". Such groups tended to pick songs,that suited their style of music, from all over the English speaking world.

I attend song sessions in various locations. A lot of songs will get a lukewarm even if polite reception from the tourists, but as soon a they hear "The Wild Rover" or "The Leaving of Liverpool" they literally go 'wild' - broad smiles appear and vigorous clapping ensues. They obviously expect to hear those songs so the entertainers oblige. "He who pays the piper plays the tune"

Of course many Irish also assume many of those songs are Irish, but they are likely to be people with only a slight interest in trad music. As already mentioned most Irish people have little interest in trad, even if it does have a strong minority following. Just tune across the radio dial when in Ireland to hear what people really like. Or go looking for a trad session in any provincial non-tourist town on a weekend - you'll be out of luck in most places.

Slán