You're Simply Wrong
For a civil war to take place it has to be ONE country. It was NOT. The reunification elections NEVER took place, so no single country could emerge. By definition that makes them two sererate and distinct countries, Viet Cong or not.
btw, Vietnam was hardly EVER a single country, going back a LONG LONG way. It had a long history or being divided, so it's not like it being "one" country should be taken for granted by any means, at any time prior to 1975. And that would be necessary to make the claim that it was a civil war. But even more specifically it was simply NOT "one" country at the time JFK moved troops there to live up to our mutual defense agreement with the South.