There have certainly been wars in the name of Scotland since 1500, the Jacobite Rebellion being the prime example. A classic case of a Union suppressing an uprising. Ditto the Easter Rebellion. The constituent states may not have rebelled, but such uprisings are usually in their name. When the states themselves rebel it means civil war of course, witness the bloodletting of the US one.
I take your point though. Usually these uprisings occur in the early years of Unions. Hence they need the means to supress them from day one. The Red Army and the PLA were thus in place in good time to ensure and defend their respective regimes.