I lived in Papua New Guinea for two years, where linguistic diversity is higher than any other country. There was however a few languages that everyone spoke. Tok Pisin was a pidgin language spoke by almost everyone, and English (due to it being the language used in schools) ran a close second. Despite the relatively few languages spoken in Europe, we don't have a universal dialect that everyone understands. The vast…
Just from personal experience, people in the nordic countries generally have a near-native command of english. In French and Germany it's a bit hit and miss, but younger people generally speaks english well enough to be able to communicate. In Italy it's pretty bad though, you can tell that just by all the signs with engrish.