it’s implicit in mainstream conceptions of nationalism/national liberation that a nation can attain the fullest expression of its freedom as a nation without ‘interference’ from anyone else, i.e. in an ethnically, linguistically, and culturally homogeneous state. like that’s the ideal venue for free expression, cultural flowering, etc.
Not everyone has the same experience as you, and not every Nationalist is a cultural-isolation-maximizer.
The Japanese have managed to remain Japanese while changing, flowing, adapting concepts from around the world, and they have an entire subset of their syllabulary used to represent foreign loanwords.
And yet… the lack of crime, the lack of Islamic terrorist attacks, being able to trust children to ride the train to school, carefully queuing up to receive supplies in the wake of a massive natural disaster… in other, more multicultural places this either isn’t the case, is only the case for the wealthy, or is enforced by the iron hand of a soft authoritarian state.
Culture is a wave, not a water, but that doesn’t mean we have to blur all of them together. Diversity isn’t a terminal value.