No it's not. A civil war is described as when one faction of a country be it religious, cultural, or racial enters into violent conflict with the governing powers of said country with the intention of overthrow of said governing powers and the institution of their rule and power. There was nothing remotely happening in the South in the 1860s that could be called a violent uprising or intention of government overthrow. The Confederacy was defending it's soveriegn existence from the invasion of a foreign power.