What's the problem with "white supremacy" in the absurdly broad sense you're using as opposed to the equivalent supremacy of every other race and culture?

Can't really think of many other forms of supremacy which killed and enslaved indigenous people around the world.

Culture is the totality of your way of life and way of thinking, you yourself are nothing but a creation of culture, the beliefs which motivate you to make these very arguments are themselves cultural conditioning.

I think I've been exposed to more cultures than just "New Zealand culture". Especially in this day and age.

If you actually rejected the attribution of value to culture you'd never bother making these arguments in the first place because the shit you have to say is no better than the shit I have to say according to your own cultural beliefs.

It's far more complex than that. I'm not a product of solely New Zealand culture.