The US attacked Iran because Israel was going to do so anyway. If they didn't attack, that missile wouldn't have killed 150 schoolgirls. Sure, the target was a mistake, but mistakes happen when you shoot thousands of missiles and drop thousands of bombs. If they had not attacked, the girls would be alive.
If Iran hadn't funded and supplied Hamas who then attacked and killed how many people (how many were little girls who were murdered and raped by Hamas?) then Israel wouldn't have had to bomb Iran.
You can go back and forth on who did what first but it ultimately accomplishes nothing in this scenario.