Because all you've said so far is, it's based on their appearance - ie, the appearance of being white. That's a tautology.

Except, I never said that. Though it's fair to say. My focus is underlying genetics. I simply noted that skin color has an extremely high correlation with respective races, at least for what's considered white, black, asian, and thus it became a logical shortcut to use those terms to describe broader races. No one who's sane thinks "it's only skin deep" except the average shitlib or leftist who's fanatical about denying the existence of race/genetics, who deploys a straw man focusing only on "skin color" for the purpose of being duplicitous or because they're really that stupid.

What part of likely similarities in their genetics would be unclear to you, compared to groups much further distanced (e.g. blacks)?

You're confusing small scale genetic differences in cultures with large scale genetic differences in cultures. For one, those two groups, left to their own devices, will obviously have far more in common with each other in their primal cultural tendencies (societies/cultures their brains/bodies are capable of forming and may form, down to basic lizard-like proclivities and tastes and inventiveness and survival ingenuity) than they would to sub-saharan blacks and aboriginal cultures left to their own devices. Culture is downstream from the animal's governing genetic potentials (the spectrums thereof). Shared experiences are even further downstream. Members of the same family won't even have all of the same shared experiences, so points about "ancient empire" and such are highly tangential to these larger facts: what may seem like small genetic differences in DNA that portray races have actually lead to very different peoples generally. You can go ahead and observe the similarities and differences between groups at whatever scale you choose, micro to macro, and see for yourself.