We US Americans had one civil war -- European and British history is of wars for over 1000 years -- good luck getting along
Europeans are very nationalistic as compared to how we feel loyalty toward the state we live in. The EU is not a nation the USA is a nation sharing a common language and culture with regional differences. In the beginning of the USA the states had some minor border wars but not wars of culture or ideology with the exception of the civil war or the war between the states as we call it.