I have the older edition and it's a great animated film. I use it in my teaching. I won't say too much, because I don't want to spoil it, but I have to say that for me, this is *not* an anti-war, let alone an anti-American, film.
I would also encourage you or anyone else viewing "Fireflies" to read "Leaves From An Autumn Of Emergencies: Selections From The Wartime Diaries Of Ordinary Japanese" by Samuel Hideo. It helps a lot to understand the historical context.
thanks