I'm really not sure this is accurate, you're looking at a caricature of a society (China Town), there is selection bias in your example.
Also think about your example of a white person moving to another country. Is that country still majority white? To make an equivalent argument you need to look at white communities in east asian countries or African countries. Do those examples support this position?
Is that really the question? Framing it us vs them doesn't help either group. This is not a zero sum situation where you defect or don't.
But I don't think this question is worth considering because considering loyalty to country is like considering faithfulness to a religion. It doesn't put you on the right side of morality. People like me don't draw that line based on place of origin.
I would hope NZ would not take the same route that so many countries around the world are taking and take on identity politics. So far we seem to be doing on average better than that.