Omg. Stop it.
First, I actually watched a video of a person who lives in Japan and they asked native Japanese what they thought about the film. Some said, they love a white woman like Scarlett. But others expressed that it would have been nice to have an Asian American in the role. And others, also thought it was abhorrent if the rumor that Japanese Americans couldn't try out for the role was.
So, even in Japan, you have a difference of opinions. And the experiences of those who are Japanese vs Asian Americans should be viewed as difference perspectives, not an excuse to belittle Asian Americans.
Japanese Americans, fall under the Asian American umbrella. And people, including Asian Americans, wanted a Japanese person for the role. It wasn't any asian will do.
(And, I had to struggle through this, who uses SJW in a serious context, especially to undercut Japanese Americans who deal with a totally difference experience than those living in Japan, it makes zero sense).