The United States of America: an Illegitimate Nation?

One of the core principles of our founding was the "Consent of the Governed."  Lincoln's War of 1861 - 1862 ended that principle.  We are today a nation composed of conquered territories, most especially the Southern states and the State of Hawaii.

Lincoln, by brute force, ended the voluntary Union of free and independent states, and replaced it with an involuntary union of coerced states.

So is the USA a legitimate nation today?  I think not.  This is not to say that it could not be restored to what the Founders intended.  The Kennedy brothers have a new book out called "Rules for Rebels," in which they advocate non-violent but non-traditional ways to fight politically for that restoration.  I am reading it now.