Additional context:
Native speakers of my mother tongue do not all understand each other due to some pretty extreme dialects. Now that I’m in Europe, I’ve noticed multiple instances of people sometimes not understand the dialect of someone from a village 10-20 km away…
In contrast, for example most American, British, and Australian people can just… understand each other like that?? I never thought much about it before but it’s pretty incredible
My guess was that it was probably due to Hollywood, but some form of mass communication, almost certainly.