About 12% of American workers are unionized. So where are these flaming hotbeds?
Unionization has been in decline since the 1950s, but at one point it was quite a significant component of the work force. The areas where Unionization was quite strong are all Democrat strongholds today.
I guess you don't have a broad knowledge of American history and the social dynamics and demographics of different areas of the country during the different periods.
I try to keep up with it because you never know what piece of knowledge will give you some insight into why something happened the way it did.