9/11=terrorism?

The bombing of Hiroshima and Nagasaki killed at least 100000 civilians. These were not military targets. Japan was a military dictarorship at the time, the people had not elected the people in power and had no authority to sway them in any way, and therefore not responsible for any action that regime took.
They were not warned that their homes would be bombed by a weapon that their shelters could not protect them from.
How would you defend this without justifying the attack on WTC on 9/11?

"The Japanese had, in fact, already sued for peace. The atomic bomb played no decisive part, from a purely military point of view, in the defeat of Japan."
-Chester W. Nimitz