As a point of order, US states do have citizens. As a US citizen, I'm also a citizen of the state in which I reside.
As a point of order, US states do have citizens. As a US citizen, I'm also a citizen of the state in which I reside.
That you can move to another state and claim residency there implies what residency is, transient, whereas citizenship is permanent.
Also, the fourteenth amendment says "All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside."
My dictionary [3] has many definitions for citizen, none of which are very specific about being ascribed to a country, although the example does use a country:
> 1 : an inhabitant of a city or town especially : one entitled to the rights and privileges of a freeman
> 2a : a member of a state
> b : a native or naturalized person who owes allegiance to a government and is entitled to protection from it
> // She was an American citizen but lived most of her life abroad.
> 3 : a civilian as distinguished from a specialized servant of the state
> // Soldiers were sent to protect the citizens.
[1] https://economictimes.indiatimes.com/nri/visa-and-immigratio...
[2] http://blogs.reuters.com/india/2009/10/02/why-is-china-issui...
The term state in that context means country, which is why citizen is a synonym for national. in the Oxford English Dictionary, that is the first definition, and secondarily (and more historically than anything) it refers to citizens of a town. It might be in use locally, but I have never heard anyone use the term citizen in that way other than poetically, and I have spent time in a number of English speaking regions.