Really? Because the three Civil Wars we've had on this side of the pond have been anything but that!

The Anarchy (1135-1153) and the Wars of the Roses (1455-1487) were dynastic disputes between rival branches of the same family. The English Civil War (1642-1651) was a dispute over governance and religious freedom between different parties of the same ethnicity.

The American War Between the States and the Spanish Civil War were both about politics and governance, not ethnicity.

I'm not saying that there are no ethnically-inspired civil wars such as those in Rwanda and Yugoslavia, just objecting to your sweeping statement.