First, "the last 200 years" is not the same as "200 years ago".

Second, history is what shapes cultures and people's views of the world. You cannot discuss and hope to make sense of what's going on in a country without understanding its history. The BLM movement, arguments about links to slavery, China's international policy, just to name a few, are all stemming directly from events that occurred in the past and continue to have an impact to this day.

And lastly, there is nothing wrong with nationalism when it means defending your own people and sovereignty of your own country. That's what all countries do and in fact is the basis of the existence of countries.