That is a great comparison! There are people who can't understand heavily-spoken Scots English, African-American Vernacular English or Cajun Vernacular English,

That is a great comparison! There are people who can't understand heavily-spoken Scots English, African-American Vernacular English or Cajun Vernacular English, and while all of those are English, they're different dialects. All are proper English, as any linguist will tell you, but Scots English is more or less mutually unintelligible. AAVE is relatively understandable because of pop-culture, but without previous exposure to it, someone who didn't have any influence to it would be confused in an environment that heavily uses it. And if you got sat in front of a Cajun family, despite the relative amount in common with them, linguistically, you'd be bewildered at some of their heavily French-influenced vocabulary and structure.