Though there's typically a common dialect variant everybody speaks, usually the one spoken by the largest city in the region.
E.g. every middle-franconian understands Nuremberg franconian dialect and is able to talk in a way they would understand.
My cofounder's wife, during a parents together at school, was "advised" by some of the mothers to not "hang around those" mothers because they're stranger folk. Turns out, they lived 1.5 miles away in the next village.
My ear has just gotten to the point of noticing German dialects, and spotting the quizzical looks of other German/Austrian/Swiss people in the group
Fascinating. I feel like they had 1,000 years to resolve this
In any case, communication technology (trains, TVs) is a greater determinant of dialect than government.