Not sure if this is the right sub for this question. But Canadians and Americans sound much more like each other (generally speaking) than like English speakers in the UK and Ireland. Of course there are different dialects all across North America but generally, they sound notably different from European Anglophones.

Southern hemisphere Anglophones tend to sound much more noticeably "British" than English speakers in North America. Obviously Australians etc. do not sound identical to Brits, but one can hear the similarities and it seems to be a more natural evolution from a British accent than a North American accent. Why is this so? Why did the accents evolve so differently?