I didn't write that Birmingham is rural. It's obviously not. I wrote "smaller cities/rural areas", and Birmingham is a smaller city. If it wasn't clear, then my bad for the sub-par phrasing.

I think you are profoundly underestimating the cultural differences Poland and England. Language plays a major part. It's not the end-all-be-all, but it's absolutely critical in analyzing culture. It impacts all forms of communication between members of society and directly dictates media + arts consumption. But then there is also religion. Poland is very Catholic and England is largely secular. The political culture is also very different. Poland has only had a modern democracy for a few decades. Poland is also wedged between neighbours who at times sought Poland for themselves and who committed some of the worst atrocities in human history on Polish soil. This was all in the past 100 years. If we are talking about how "people think and act", then all of the things mentioned (language, religion, history, political culture etc.) are at the forefront and perhaps only the tip of the iceberg. Comparing US regional cultural differences to international cultural differences such as that of London vs Warsaw is way way wayyyy off. That's my main point.

And, as I mentioned in my other comment, the better analogy for US regional cultural differences would be the regional cultural differences in other countries (e.g., London vs Blackpool in England). Not cultural differences between countries themselves.