Certainly an angle one could explore, but personally don't find it convincing. North Dakotans are so similar to other Americans elsewhere in the US that to me the most obvious factor is the infuence of American culture on people that grow up there.

I also base this on what I see in modern times of how immigrants change. E.g. Americans who come to Norway do get significantly changed in their views and perspective. It applies to anyone who is an immigrant. I live in a neighbourhood of Oslo dominated by immigrants.

Second generation Pakistani, Tamil or Vietnamese immigrants here are profoundly different from their parents generation. The most clear thing is the adoption of Norwegian cultural norms and values. That is a pretty universal thing. Immigrants adopt the values and cultural norms of their host country. They same would have happened to Norwegians in the US.

I can even see that already partially on one of my relatives living there.

But I also think the values, cultures and preferences are way different today and in 1870. Both Norwegians and North Dakotans today are very different today from what they were back then. People have been profoundly changed by the economic, technological, cultural and social changes which has happened since then. The US has very different laws and political instututions compard to Scandianvia which is going to lead to very different political and ideological development.