撃ちうちてよ
アツツのサイパンの仇を
亜細亜十億の為に
It sounds funny to me, so I would wait until Toritoribe-san jumps in, or some other native Japanese speaker. It (presumably) means "Shoot at the enemy in (hot?) Saipan, on behalf of 1 billion people in Asia".
撃ちうちて feels like an unusual repetition.
アツツのサイパン or possible アッツのサイパン ← hmm, sounds weird to me. "Hot Saipan"?
亜細亜十億 Presumably means Asia 1 Billion people, but the "people" part is missing. Not unusual to drop words in Japanese when the meaning is understood from the context, but this omission feels weirdly egregious to me.