“So what citizenship would you have had if you were alive and living in the United States prior to its organization under the Articles of Confederation?”
You mean after the revolution started, while the states were united under the Continental Congress, if that is, in fact, called “the United States”? You would be a British subject in the eyes of the British before the war was settled. Aside from that, a citizen of your home state.
I’m not sure whether the Continental Congress was organized enough for the citizens of the states to also be citizens of the congress. Certainly there was no Constitution or Articles to bind the states together. There was the Declaration, but that did not bind them in the same manner.