I'm not aware of when or how Lee formally relinquished his U.S. citizenship, and it would not have been taken from him until 1864.
Either way he was not a US citizen, I agree.
He would have been for at least three years, during which he was engaged in war against the United States, dual 'citizenship' notwithstanding. And I think there are some questions as to the Constitutionality of Section 14 of the Wade-Davis bill to begin with.
I think the CSA was an independent country, but as YOU are apt to hiss, if the CSA didn't exit, then what was Lee's citizenship status after 1861?
From 1861 to the summer of 1864 his status was U.S. citizen. From 1864 on his citizenship was stripped so he was actually a stateless person.
No, he wasn't. Virginia left the Union on May 23, 1861, and by secession, all citizens of Virginia, of whom Lee was one, ceased to be citizens of the United States.