Empires, essentially, create order. In their absence, you don't end up with lots of happy, little nation-states full of people sitting around campfires singing John Lennon's "Imagine." What you end up with is civil war, anarchy.
I refuse to accept that Western civilization is like some hopeless old version of Microsoft DOS, doomed to freeze, then crash. I still cling to the hope that the United States is the Mac to Europe's PC, and that if one part of the West can successfully update and reboot itself, it's America.
In the old days it would have been a relatively simple matter to have checked Hitler's territorial ambitions. All you'd have needed would have been the 1914 combination of Britain, France and Russia. Indeed, if such an alliance had acted decisively to defend Czechoslovakia in 1938, Hitler might even have been overthrown by his own military. But it was not to be.