My take. WW III is a better chance of happening than a new Civil War. BUT... If the World War comes up as a defeat for the USA (War might only be for a year or two) with a UN settlement and no nukes. Then, the nation will be shattered and the people want scapegoats for the defeat—That’s when the civil war comes. The Axis would love to see America cut into several nation states to never dominate the Earth.
World War will trigger Civil War here. This isn’t 1941.