When Americans say Europe they usually mean Western Europe, which is not really how the rest of the continent is. For instance in Mediterranean or Balkan people (and kids) are anything but quiet.
Before coming here I visited and lived in many European countries and Italians for sure are the loudest in public settings (restaurants for example) - especially when there are many of them together. From my experience from Greek Islands Englishmen are the loudest of all - at home in England they are quiet and polite though . Germans are the quietest ones when traveling to other countries but loud at home sometimes.
All this is totally my subjective point of view of course.