Colgate v. Harvey

This case spells out this very nature of the “U.S. Citizen” political status that when bore is paramount and dominant to state citizenship status. This is further backed by the definition of citizen, where its mentioned that citizens of the Federal Government were not considered state citizens in federal courts.

https://supreme.justia.com/cases/federal/us/296/404/
Thus, the dual character of our citizenship is made plainly apparent. That is to say a citizen of the United States is ipso facto and at the same time a citizen of the state in which he resides. And, while the Fourteenth Amendment does not create a national citizenship, it has the effect of making that citizenship "paramount and dominant" instead of "derivative and dependent" upon
state citizenship. "In reviewing the subject," Chief Justice White said, in the Selective Draft Law Cases, 245 U. S. 366, 245 U. S. 377, 245 U. S. 388-389:

"We have hitherto considered it as it has been argued from the point of view of the Constitution as it stood prior to the adoption of the Fourteenth Amendment. But, to avoid all misapprehension, we briefly direct attention to that [the fourteenth] amendment for the purpose of pointing out, as has been frequently done in the past, how completely it broadened the national scope of the government under the Constitution by causing citizenship of the United States to be paramount and dominant, instead of being subordinate."