In terms of internal disputes turning violent I would point you towards the various religious wars, revolutions, and civil wars that have ripped Europe apart.
Even as late as the 1920s Austro-Hungary and Russia had their remains ripped apart by internal violent struggles. Certainly some European states have enjoyed relative prosperity and peace (the UK springs to mind as the readiest example, but even here you have the Irish War of Independence and The Troubles).
Really I'd say America is actually more stable than Europe has been since the Indian Wars really began to die down. Even before that it has a better record for major internal conflict than any major European power (US Civil War ended 1865, every major European nation has had one of some description since then).
You are however, perhaps right about regional identity. Certainly some areas of America are far more different than equivelant European nations. Texas compared to New England is far more different than Scotland and England for example. However, I'd not that even in Europe you have strong national/regional identities in many places. See for example Northern Ireland, Kosovo, etc...