Funny how this works in different countries. In Germany every region has a regional dialect. My daughters grew up where the natives speak "Allemanisch," which is very much like Swiss German. In the valley, less than an hour away, where their mother was went to college they speak "Badisch" which is more similar to the Alsatian dialect spoken in France than to Allemanisch. My daughters were raised by people who spoke Swabian (from the area near Stuttgart) or Platt (from the area around Cologne), so they understand most of the dialects, but only speak High German. That's good for me because I really only understand well when I am hearing High German. When they switch to dialect--any dialect--I understand, as they say "nur Bahnhoff".

Meanwhile, in the US the two languages you hear most frequently are English and Spanish. Both are spoken with lots of accents, but encountering a dialect that natives can't understand is very rare. I would have thought that Britain was somewhere in between, until I tried to make sense of road signs in Wales...