Which European language group is the most diverse one, culturally?

[Mikula]

Romance thanks to the conquistadores. However Slavic is a close runner up, especially if you take Russia into account. Many non-ethnic Russians speak Russian as their first language basically.

It's just not that densely populated as South America in its entirety and parts of North America at that.

I mean whether is, for example cultural difference between Swedes and Austrians , larger than difference between Portuguese and Romanians or Czechs and Bulgarians.

[Ülev]

славѧнски

[Damião de Góis]

Even in an european context i see plenty of diversity in the romance world. From walloons to Sicily, from Portugal to Romania...

I think the distance from Portugal to Romania is larger than the distance between any slavic country.

[Bobby Martnen]

It's a good question, but I don't have the answer.

Sorry

- Bobby

[TheForeigner]

Slavs without a doubt.