A lot of people think the term “Nation-State” is just another synonym for the word “Country”. Hence, why many people would say “yes, US is a nation-state” and some people even use the Montevideo Convention to say US is a nation-state. But that’s not it. Nation-State isn’t just some another fancy word to replace the word “country”, it carries a more deep meaning.
In simplified explanation, a Nation-State is basically the direct opposite of a Multinational State (see what i did there ?). You might hear another name for multinational. Now, a Nation-State doesn’t instantly means the lack of other ethnicities within the territory of such nation-state, that’s just unavoidable (except for the case of North Korea where basically 99% of its population are ethnic Koreans). A Nation-State is basically a state where a great majority of its population have something similar or something in common. It could be language, it could be shared history, it could be blood, etc, etc. You hardly can call a country like Austro-Hungary a nation-state since every single ethnicities inside of it hating each others. Everyone want nothing to do with each others’ cultures. A Nation-State is basically a state that is the “Homeland” of a nation. The term “Nation” is referring to a “group of people”. Some people say that the word “Nation” is even a synonym to “ethnic group” but i digress.
Also, the word “homeland” here is also not just another word for a country. It’s the same concept why the word “House” and “Home” each have different connotation. Homeland basically means that a land is where, again, the home for a nation since “time immemorial”. Germany is the homeland for ethnic Germans, France is the homeland for ethnic Frenchmen, England (and by England, i mean England, not United Kingdom as a whole) is the homeland for Englishmen, Denmark is the homeland for Danes, you got the idea.
Note that many of these countries are named after certain specific ethnic group. The word “England” came from Engla Land, which basically means the Land of the Angles. English people being descended from the Germanic tribes that migrated to the British Isle: Angle, Saxons, Jutes, and with an addition with some Frisians. Denmark is also named after a certain specific ethnic group called Dani or Danes, hence the name Denmark. Etc.
So with all of this information, is United States a nation-state then ? Personally, i’m not really sure. I would think US is not exactly a nation-state since it is not exactly tied to a specific ethnic group. You would probably think US is tied to Anglo-Saxons or the English (which in some case true), but you’d be amazed that i read lately that the largest ethnic group in US is Germans.