I’m afraid I’ll have to disagree. I have read the articles, like this one stating she was never imagined being cast as Japanese actress. In articles I’ve seen - like the one linked above, the creator doesn’t say “Motoko isn’t Japanese” but that they had never envisioned her being played by a Japanese actress. The fact of the matter is, regardless of whether she “looks” Japanese - because yes, she is a cyborg - the Major’s identity is Japanese, and female. Her worldview, her cultural associations, her language, frames of reference, and the nation she serves...they are all Japanese. To be frank, the themes of the work are more to do with post-modern society, reproduction, self-identity, the reality of memory, and the connection between brain, self, and body.
When asked why she does not choose a stronger, more imposing body, Motoko claims it would feel “wrong”, and dislikes switching shells. While the cyborgs in GitS do, in fact, look more “white” than the average Japanese citizens portrayed in the background, they do NOT look European. Europeans look European in GitS, and the cyborgs look almost surreal, compared to the “flawed” human bodies of any race.
The issue with the casting of Motoko is not that a white actress couldn’t LOOK like a cyborg. In a world where there was equal opportunity for all actresses, regardless of race, it wouldn’t matter as long as the role was performed well. But we don’t live in that world, and that means Motoko Kusanagi should be played by a Japanese woman. In an industry where studios seem to do anything possible to avoid casting anyone who isn’t white, This. Is. A. Problem. If films set in Japan, with a majority of Japanese characters, can’t cast a Japanese actress as the lead, then what films WILL Hollywood cast such an actress in?
Another kung-fu movie, you say? Ah. Stereotypes it is, then.
As far as your opening statements about a racially ambiguous Japan in GitS, I am left to assume you have not read the manga, or watched the numerous movies and anime, in which the conflict between Japan and the west, and Japanese traditional values and technology, are incredibly strong motivating forces for the characters and plot. You see, it doesn’t matter that Motoko doesn’t have “parents’ or “flesh”. She is a cyborg but that doesn’t make her less Japanese.
In the end, the issue is really that Motoko’s role could have gone to a Japanese actress, and didn’t. Instead, a silly plot device was used to excuse the choice of a white actress to play the leading role of a film whose main character is a Japanese woman.
(As an aside, I’m not sure why you chose AoT as a counter-example. it seems you may also have missed the point of Attack on Titan - which had a live-action movie made with a European cast because it is explicitly set in a world where (apparently) only a single Asian bloodline remains. The characters in AoT ARE, in fact, European, and their story is set somewhere in Europe...as opposed to GitS, which has explicitly Japanese characters, set just as explicitly in Japan.)