[cutemonster]

Why don't they say "country"? Or just "nation"?

(Can it really be because "nation state" is more fancy?)

I can understand, though, why they don't say "state" -- maybe that'd sound as if a single state in the US had attacked

[peteretep]

I think this derives from “state-sponsored”. “The state” has a distinct meaning from country or nation which I think is important to capture too.

I think your point about confusion with constituent states is spot on though