I hate to disagree with Dr. Williams, but the United States did not start with the ratification of the Constitution of 1786. The Declaration of Independence was a collective statement (”...in Congress assembled...”), asserting a combined and United sovereignty and independency. Some colonies/states did issue individual declarations as well. Congress the formed the United States under the Articles of Confederation. Which called for a permanent union. The Treaty of Paris was signed with this United States, not with each ex-colony.
The Convention of 1786 was called under the authority of the Articles of Confederation, to amend them. It was not creating a government de novo, but reforming an existing one. This is shown by the ratification process prescribed. The Constitution becomes effective when ratified by 2/3 (?) of the States, and implicitly becomes binding on all the United States, including any which had not yet ratified it. Had the intention of the Delegates been otherwise, the Constitution would have gone into effect as soon as ratified by any two States, but applied only to those States which ratified it; the rest would have continued to be governed under the Articles of Confederation.
On the original question, although the Constitution defines treason as making war on the United States, the government did not choose to prosecute any of the generals of the CSA as traitors, indicating that as far as they were concerned (at least the majority), they were not.
” . . . and implicitly becomes binding on all the United States, including any which had not yet ratified it.”
That is an interesting comment. May we see your data?