Confederates at FT Sumter

There's a slight, but I believe important difference between the two situations. fort Sumter was indeed a union fort, but it was deep within Confederate territory and the CSA just declared itself an independent nation. It could be argued that the Union was illegally occupying the CSA and were expelled with force.

Pearl harbor was US territory amongst US held space. Unlike fort Sumter, you cannot claim that the attack on Pearl harbor was defensive.