[magpi3]

The conflation that is happening in this thread is between culture and ethnicity not nationality and ethnicity. When someone of mixed race says they are "all Japanese" they are obviously talking about their culture and not their passport.

[sridca]

Culture is tied to nationality. Do you have an example indicating the contrary?

[magpi3]

Of course. Nation states have not been round that long. Just a few hundred years.

Jewish culture exists throughout the world. All religious cultures actually. Islamic culture.

Immigrants often retain many aspects of their culture when they move to a new country.

The US itself is a huge mismash of different cultures. People in the US are not bound by a single cultural identity. They are bound by the constitution and the principles and values it represents.