[vurpo]

I think it's actually that human cultures are infinitely nested, with every group containing subgroups with some level of disdain towards each other. Conflicts on a higher level often seem to "override" conflicts on the lower levels (although I don't know how often this actually is true). For example: I'm from Finland, and if our team plays hockey against Sweden it's as if there's a war against them or something. However, if Sweden plays against Canada you'll still see people cheer for Sweden over here.

I believe this reveals the existence of a tree-like hierarchy (very loose) of human cultures, and I also believe it goes way lower than just the country level (all the way down to individual people). xkcd also said it a long time ago: https://xkcd.com/1095/

[wahern]

I agree, national enmity is a manifestation of a broader phenomenon. Part of that broader phenomenon is that identity is typically defined, at least in part, in opposition to another group. And identities can nest, intersect, etc.

In context of island erosion, this poses the question of whether a nation without any territory can exist purely in opposition to another similarly situated nation (i.e. both sharing a positive history that is indistinguishable within the context of a broader society to which they've emigrated). And that creates an interesting ethical dilemma if the goal is to preserve national identity, especially one that has been "victimized" by [perpetrators of] global warming.