When I was younger, I moved from the US to Canada. Back then, I used to think countries are countries because people share the same language and central culture (as well as being largely contiguous). I came to Canada expecting some massive culture shock but I was surprised to realize it was basically the same. I used to advocate for the union of the US and Canada into one glorious first world, absolutely massive nation with the possibility of Québec leaving to be its own country. People didn't like my idea. I thought it made sense, 1 country, 1 language, 1 culture, that's how the world should be. In my mind I saw Canada and the US as one nation divided by history and hesitation to change.

As I grew older though, my opinion on states started to change. In high school when they have diversity day or whatever, different cultures are represented by countries. In everyday society, that's also the view, nationalities = cultures. However, as I looked into the demographics of various countries, I realized that the truth wasn't so clear cut at all. 1 country, 1 culture, 1 language was far from the norm. The current borders that exist in the world exist largely because of war, conquest, mandates, etc. The national identity of a lot of these nations were usually constructed afterwards in order to solidify the unity of the state, not the other way around. Even the ones that are fairly culturally similar are so because regional uniqueness were repressed and/or people assimilated, deported, or killed. Some ethnicities and nations that have a strong identity today used to be loose collections of tribes with no significant previous sense of a unified identity. The states of today are usually in their current forms because of momentum above all other things.

I also realized that the concept of nation wasn't as clear cut as I thought it was. Language is not the be all and end all of nationhood. Neither is religion or culture. A national identity can be based on any combination of language, culture, shared history, religion, lineage, customs, traditions, caste, tribe, clan, or even just living in the same country together long enough for them to be used to it.