Ah, I read your post on Mouryou no Hako and thought it looked really interesting. I'll definitely have to see that one, it sounds like it raises some important issues. In fact, I just read a book called The Attractive Empire: Transnational Film Culture in Imperial Japan by Michael Baskett, and he also argues that even in the postwar period, the "imaginary of empire" persisted in Japanese film, especially in victimization films that "recognized that the Japanese military had been wrong to advance into China, but also subsumed Asian suffering into the larger cauldron of human suffering, relieving individual Japanese of the need to remember themselves as aggressors." (To be fair, he also notes that the drive to imperialism was felt all over Asia, even in colonized countries like Korea. So you're right, it's not just a Japanese thing.)

Now, do you think anime that depict Japanese imperialism in Asia, even in passing as in Millennium Actress, work against this sort of sanctioned national amnesia? They may not be able to include non-Japanese perspectives (I'm not sure they could without risking accusations of appropriating the voices the formerly colonized) but they are a little more aware of Japan's history in Asia than Gen and even Grave of the Fireflies.

Also, intriguing idea about the American reception of Gen. That would be a great way to start looking at it from a transnational rather than just nationalist perspective!