People traveled over for a complex set of reasons. I think that one should be careful about feeding too much into beloved national mythology. We all have those in every country. I think in America people love to believe that America is made up of the bravest and most daring cohort of people. No doubt emigrating to America was a bold move, but I don't think one should overemphasize that as the primary reason. First and foremost it had to do with material conditions. When Norwegians began emigrating to the US in the 1870s it was not due to Norway being exceptionally poor then. Quite the contrary Norway had developed into one of the more prosperous countries in Europe. However Norway experienced a great economic setback among farmers. People tend to accept the conditions they know. What people really dislike is seeing things get worse. That tends to trigger action. Really poor people didn't have money tro travel. The Norwegians who left were people with some decent income, but which had simply experienced major setback.
Just to make some remarks on language. It is one thing what you speak within the family, but a lot of what language is about is the literary tradition you are part of. North Dakotans whether they spoke some Norwegian at home or not did fundamentally get cut off from that. They were not going to be reading Norwegian newspapers, books, go to Norwegian theatre etc. Thus values and cultural influences would come from a wider English speaking America. Of course in the early years there were some local immigrant newspaper written in a mix of Swedish, Norwegian and English, but very little of that remains today.
I got to say I am puzzled by the remarks on racism. I think you are the second person to remark on that. It is odd to me because I don't actually discuss racism in that story at all. I did not say a single word about North Dakotans having prejudice or being racist. I certainly met racists there, but that was never discussed in my article.
What I talked about is the common American propensity to racialize, meaning attribute various traits, values and behaviors to people of particular skin color. This thing is so pervasive in American society that I think Americans have become totally blind to it. It has become so normal that they don't even see it anymore. All sorts of surveys, research etc will be based on dividing people by race. Checking a box for your race is a common thing in the US. For that reason a lot of research and analysis is done by using race as a distignuishing attribute.
When discussing politics US media will be focused on how well a candidate does among people of a particular skin color e.g. When discussing diversity in the US, it is almost exclusively implying diversity of skin color. It is just an observation about American pre-occupation with race. It is not the same as saying Americans are racist. Many of the people focused on race are actively fighting against racism.
Although it seems like a hard thing to break out of when the American-English language itself has itself been so hardwired into this race thinking. I could mention e.g. that the word "race" doesn't really exist in Norwegian. We have the word "rase," but that isn't used about people. The modern American concept of "race" doesn't exist in Norway or much of Europe. Every time, I remark on that, Americans think I am saying racism doesn't exist in Europe. But the existence of racism isn't predicated on the existence of a particular word.
One could of course say that racism works in different ways in nearly every society. I remember reading about a Black German going to the US thinkig she would find so many people that could relate to her struggles. Yet, she found that racism and the experience of black Americans was too different from her experience for them to really have much to share.
There are people from former Yugoslavia surviving genocide and ethnic cleansing, who come to the US and get told they have white privilege and know nothing about discrimination and racism. That is because in the US racism is almost only about skin color, while in Europe it is a far more complex mess.