Tokyo Bay was not the property of the U.S. Fort Sumter was.
...and no one was killed at Pearl Harbor.
Ah, so if the Japanese had sunk all those ships and bombed all those airplanes and had, through some miracle, not killed anyone then it'd be OK?
What about the US warships that were sent to supply Fort Sumter? Were they not in South Carolina waters? Is that not an act of war?
You can read any number of sources and come to the conclusion that the firing on Ft. Sumter did not push the border states into the Confederacy. The border states were willing to stay in the Union provided the cotton sates were not coerced into staying. The planned invasion of the South forced the border states to make their decision. If a Union soldier would have asked a Confederate soldier why they fought, the great majority would say “because you are here.”
The fact is, the federal government lost the consent of the governed in those states that seceded.