It's troubling when individuals do this, but I find it especially brutal that "double down and never admit guilt" is the go-to strategy for most nation states and corporations.
edit: Wikipedia says there are around 20 nation states. I don't know why you're picking those out specifically though.
Meanwhile, does "nation state" apply to the Plurinational State of Bolivia?
"Nation state" seems to be a thing because state alone could be confused with the 50 US states.
With nation state the focus is on the institutions and leadership, with country the focus is on land and ordinary people it seems.
However in the US the word 'state' is overloaded, so 'nation state' is used. It's confusing, because 'nation' is sometimes used to mean 'country' (which is how it's intended in 'nation state') and more traditionally used to mean a people with a shared language and history.
And the French and the Brits have/had a lot of "nations" which are part of their "nation" and which thus are not "nation states" of their own. For example, Scotsland (and even technically Britain itself) are both nations that are themselves part of the nation-state that is the U.K. For the French, it gets a bit more complicated, since they have a number of territories which are nominally sovereign but are legally subordinate to the French government in Paris (like Tahiti).
Also, it's my understanding that the main island is Britain, and that "Great Britain" includes the smaller outlying islands, but not the island of Ireland.
Most of the world is currently organised in nation states, but most of those are multi-ethnic. Ethnicity != nationality in this sense.
So it's used in a context like this to imply something nefarious, treating a country a bit like a dystopian sci-fi megacorp.
That doesn't make the assertion wrong. It would have been equally valid with the term "country". Just explaining (over-explaining, probably) why the OP chose that particular phrase: it has a particular emotional impact.
A state is the entity that taxes people, builds roads, maintains a military. It has a "monopoly on violence" in a particular territory.
A nation can be stateless - like the Kurds or Uyghurs. They have a cohesive self-identity, but lack their own state. Colloquially, "nation" can also mean "country" - think "national champion", but this more specific meaning exists as well.
It's rarely necessary to use the term "nation-state". Just using "state" is fine. I suspect people like using it because it has a nice ring to it and sounds serious.