Also, this truly isn't meant as offensive whatsoever, I love a lot about Japan, but anime is in its entirety per definition japanese, which means that unless it's very clearly stated, at least japanese people themselves will just look at it as japanese. Maybe a non existent magical, fantastical version of it, but still. Or so many hardcore anime fans often tell me. To rephrase it somewhat, I'm pretty sure if a live action dbz film would get made in japan, they'd cast EVERYONE with japanese people and would probably be fine with it as 'anime is japanese'. The baseline unless stated otherwise is that everything is, implicitly, set in 'the world japanese people live in', which to an outsider is 'japan', but to japanese people it's simply they're world, they;re normal cultural pov.
Maybe I've gotten a wrong perspective on how anime is viewed within japan, but I think it's truly a massive difference in cultural frame of reference. I'm pretty sure a lot of japanese people wouldn't even realise there are people out there who do NOT see Goku as clearly japanese. They'd probably be stupefied by that. He;s a japanese hero, written by a japanese guy in a drawing style per definition called japanese.
I don't think either perspective is wrong, this is all just fictional. That's exactly why your argument, though it would seem to at first glance to do so, doesn't hold up Supernaturaladdict, exactly because it is all fictional, ANYTHING is possible, including all saiyans being exactly like japanese people. The whole world could be just Japan/asia. You really think a japanese man makes up an animated series strictly in japan's own style Anime (Manga), has it based on asian cultures, and mostly filled with asian aesthetics and appearances and would look at Goku and say 'yeah, he's closest to west european..." I think not mate.
I think that's our POV as non-asian people.
The style is ambiguous and that makes it prone to the cultural interpretation of the viewer, it's that simple. The person who made it made something japanese for japanese people, there's no reason for him to view it with any different pov then that unless he explicitly meant to do so. I think he did mean to with e.g. Bulma and the twin androids, but not the main character based on an asian legend... There's no way to make a dbz film that can cater to both regions if it has to cast real life people... No way at all.
There's two DBZ's: the japanese one, and the western one. As weird as that may seem to anyone, I see no way around those parallel POV's.