Was this culturally insensitive? Are only the survivor's stories relevant? How would be a better way to present the story?
Asian Americans are just Americans who know absolutely nothing about Japan. They know nothing of the history, the language, the culture, and would probably put an eye out if asked to use chopsticks. Sorry, but I always get a laugh from "asian americans" who think that because they kinda sorta look like they might be asian (but know nothing of asia) that they have something to say about asia. Sorry, but your average taco bell employee knows more about Mexico than Mexican Americans.
One notices that such news outlets are always very careful NOT to find or interview people who think that it's just fine to have a Caucasian actress involved in the movie.
I know quite a few real Asians, and many real Japanese, and I can tell you that this probably doesn't even register as a valid question. If the Japanese want to make a movie about Hiroshima, they are more than capable of doing so. I think the original Godzilla movie took care of how they think about the atomic bombs dropped on Hiroshima and Nagasaki. For ordinary Japanese, they felt quite powerless about the entire thing. When the surrender was made, they were quite happy to have Americans take over the country because their government had failed them miserably. We didn't annex their country, but rather gave them a helping hand, and because of that, the Japanese have been the truest friends and allies. These disgruntled SJW Americans of Asian descent would be laughed out of Japan, if I'm brutally frank.