Citizen- one entitled to protection, rights, and privileges by a State.
The Confederate Constitution did not eliminate citizenship to another country. However, Bills passed by the U.S. 40th Congress, took citizenship away from the peoples of several States, for being citizens of said States. The first bill S.131 made all civil governments subordinate to U. S. military authority. Bill S. 123 vacated all the government offices of the present persons and replaced by the military as seen fit. Bill S. 126 "State constitutions of rebel states must declare that such State shall ever remain a member of the American Union, that every citizen of such State owes paramount allegiance to the United States..." S. 130 "no person shall be entitled to vote unless the requirements of said oath (to support the Constitution of the United States) are fulfilled.
Interesting, look at the requirements for the Confederate President.
"No person except a natural-born citizen of the Confederate; States, or a citizen thereof at the time of the adoption of this Constitution, or a citizen thereof born in the United States prior to the 20th of December, 1860, shall be eligible to the office of President; neither shall any person be eligible to that office who shall not have attained the age of thirty-five years, and been fourteen years a resident within the limits of the Confederate States, as they may exist at the time of his election."
Now look at the U.S. Constitution
"No person except a natural born Citizen, or a Citizen of the United States, at the time of the adoption of this Constitution, shall be eligible to the office of President; neither shall any person be eligible to that office who shall not have attained to the age of thirty-five years, and been fourteen years a resident within the United States." So if you were born in the colonies prior to July 4, 1776, you could not be president, the "United States" did not exist prior to the Declaration of Independence.