In sociolinguistics there is a concept called complementary schismogenesis that describes a mechanism that can result in exaggerated differences in conversational style. There is tendency for people with different conversational styles to attempt to pull the conversation towards their style, and when multiple participants do this, the differences become increasingly exaggerated.

For instance, if an American who talks slightly louder than average converses with a European, he may start talking even louder to try to get the European to speak up a bit. The European will then talk even quieter to prompt the American to follow. Then the American will get louder, and the cycle will continue.

This is can explain how a minor difference in average actual volume can lead to a major perceived difference.

https://en.wikipedia.org/wiki/Schismogenesis#Sociolinguistic...

I'm American, and I sometimes ask myself that too: I catch myself talking loudly and I have no earthly idea why. Probably because that's what everyone else is doing!