This question is awesome! It’s certainly not the most contentious question I’ve received, and I feel like you’re not coming from a negative space, so that’s cool. It’s also something I’ve been thinking about lately (and discussing with other multiracial women). I don’t want to be reductive, but I feel like it can be summed up in just a few statements really:
1. Despite being partially white biologically, I benefit from almost none of the privileges associated with whiteness. Or perhaps it would be better to say that I face many of the same tribulations as people of colour. I’m not sure if there is a difference between the two… It basically comes down to the idea that I am automatically considered “Other” because visually I look non-white, and because I’m not a “pure-bred” white.
2. Hybridity, or multiraciality, or whatever you desire to call it, kind of operates in a space outside traditional breakdowns of what “colour” is. This makes it immediately non-white, really because of what I said above – I don’t benefit from the privilege of whiteness, so I am negotiating a space separate to whiteness. This space is governed by literal factors like having non-white skin, as well as more abstract factors like transnational/no-nationalism. The term “PoC” seems to allow for a more abstract identity, and really includes all “Others” that don’t benefit from white privilege.
3. The One Drop Rule is critical to understanding why half whiteness doesn’t qualify as “real” whiteness.
4. I find terms like “Caucasian” problematic because of how they have been treated by anthropology, and because of how Eurocentric anthropology has been historically. If by Caucasian you mean white, then I guess my first point really demonstrates why my “whiteness” isn’t important to me – I don’t identify as a white person, despite my dad being white. I’m brown!
5. I identify as Anglo-Indian (or British-Indian), which has a lineage in a different history spawned from Colonialism in India. I don’t think about this as being a focus on one half of my heritage – it is my heritage and my history. My family are in Australia because India gained independence and there wasn’t a future there for them. Then my mum married my dad, and now I am Anglo-Indian because she is. Being Anglo-Indian is my way of identifying this Colonial history as implicit in my personal history.
6. It’s also really hard to feel like you belong to the white majority when the white majority constantly exoticises you, asks where you are from, accuses you of being tired due to natural under eye circles, etc.
I feel like I could write one million more points that expand on this question, but I have lots to do so should keep it short (or my version of short, which is sort of long).