The rest of the world makes a useful distinction between a 'country' (such as France), a 'state' (the public institutions which run France), and a 'government' (the political entity which controls the French state).

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.

As a friend in the State Department exlained, it's because of the French and the British. Generally,"nation" is used to refer to an autonomous political unit, but "nation-state" refers specifically to a sovereign nation.

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).

"Britain" is a bit confusing. Most often it is used to refer to the UK itself, or sometimes to Great Britain the island. I doubt that's what you meant.

Yes, didn't notice the error until after window for editing had passed. I initially meant England, but "Britain" itself still works because the UK includes more than just the nations on the island itself.

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.

The English language is horribly ambiguous and confused around words like nation, state, nation state, country, nationality, citizenship, ethnicity, race etc.

Yes, but I've not seen an explanation of which useful cases are covered by "nation state" but not by "country" or even better "government". I don't think it even solves the problem of countries which cause other people to get mad if you acknowledge their existence (Taiwan, Palestine)

Meanwhile, does "nation state" apply to the Plurinational State of Bolivia?

Government is also a murky concept. In the US it seems to cover all of the state apparatus, while in other cultures it only refers to the executive branch or even the "cabinet" specifically.

"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.