"have a way of turning into anthemic expressions of vicious nationalist resentment"
It's a fine line between maintaining dignity, identity or whatever after defeat and perpetuating a sulky resentment.
For example, "Flowers of the Forest" (in Jeannie Elliot's version), words more or less contemporaneous with the Hanoverian oppression of Scotland, is one of the world's great songs of the defeated.
"Flower of Scotland", on the other hand, is just a whinging cringing expression of vicious nationalist resentment.