This is an althist about if the majority of two party wars ended in armistices/formal peace treaties between the two governments.
1867: The Confederate States of America and the United States of America have signed a peace treaty, the southern states and territories now belong to the Confederacy
1867: The Confederate States of America is now internationally recognized. It has a new name: Southern Union, the US also has a new name: Northern Union
Some time in between: New States are formed: New Qing is the Southern Part of Nevada (settled by Qing China), South California is all of California south of SF, North Mexico is the northern half of NM and AZ, because of the Confederacy's donation of land to Mexico. Kansas is divided into three regions, the top for the Northern United States, the centre as a DMZ and the south to the Southern Union
1914: The Southern Union joins WWI to support the ally of the Ottoman Empire
1916: The Northern Union joins on the side of the Allies
1918: The Allies win WWI and the Southern Union loses New Qing to the RoC and loses South California to the NUSA .
1923: The Southern United States of America attack New China, and a war starts between the NUSA and China versus the Japanese Empire and the SUSA.
1926: The Southern United States of America defeat China and the NUSA and reclaim all states lost at the end of WWI.
1941: The Southern United States side with the Japanese in World War Two, but refuse to ally with Fascist Europe
1942: The Southern Union and Japan attack China and conquer Tibet.
1944: The South develops nuclear weapons and bombs Los Angeles. The city is devastated. The Americans find the technology and bomb Jackson, Mississippi
1947: WWII finally ends for the Americans and the Japanese. The North United States surrenders to the Axis powers, and the South surrenders to the Allies. The allies win the war.
1948: Japan and the United States are divided. The North is unified with Canada, and North Japan is given as a Soviet state. The South is claimed by China. South Japan is under British Control.