By that definition, the Revoloutionary generals and soldiers would be considered traitors.
In the case of the Confederates, however, they were traitors to the Union, aka the United States.
It was what it was. The Union was victorious and we were better for it.
The only positive that would have come if Lincoln had let the south go (as many New Englanders wanted anyway) is that Cuba would have likely been annexed by the Confederacy. Therefore, when, by the 1870s and 1880s, when the Confederates would rejoin the union (due to high inflation caused by the printing of fiat money, and the lack of a coherent national economic policy in general, to say nothing of the need for industry), Cuba would have been a part of the United States.
If it weren't for the traitors to the crown in the 18th century who took us to war over manufactured causes, there would have BEEN no Civil War as Slavery would have already have been ended, and the Northern Electoral Bloc could not have cut the South out of the ability to have any say in the choosing of the President.