Categorization is a problem; it can hide subjects as easily as it can find them if the categories are too specific. Your song selections I am sure I will consult often, and I look forward to the tunes and documentation, but I find the headings just get in the way.

You are correct about the original meaning of Hispania, but current usage applies to the Spanish; Iberia is the term used currently for the peninsula (Taking it back to ancient times, Iberia was a region of the Caucasus but lets not go into that). The OED defines Hispanic as "pertaining to Spain and its peoples;" rather leaving out the Portuguese. Lusitania is seldom used; combining both into Iberian seems best- but why use these divisions in the first place?

The history of Billy Barlow is pretty well covered in thread 63035 (first appeared in England, later regionalized in the U. S., Ireland and Australia with different attributes in each): Billy Barlow

I would look under Anglia for Billy (and Vicar of Bray), under Caledonia for Parting Glass, and under the wrong heading for several other songs. And where would I find Canada? (America, in Canada, means the U. S. A.). Leadfingers has already mentioned Australian songs (Irish, English, Welsh, Scottish, and etc.)