Citizen versus Subject is a concept foreign to most of the younger generations. Foreign as in it is a part of civics no longer taught in most schools. As a philosophical concept, I would venture that it is terra incognito to the vast majority these days.
There is an interesting twist on the subject, which is the trite concept of “citizen of the world.” What began with Diogenes has morphed, or been hideously misshapen, by modern socialists into something else.
This concept is discussed here, and it is well worth the read. Go read.