As has been explained into near-exhaustion, intent has much to do with a moral issue.

A bit further on the Afghan example you gave:

The military attacks enemy targets, and civilian deaths are mistakes. Terrorists carefully plan, and execute missions whose sole intent is the annihilation of non-military civilian targets.

The United States can, and did, regret killing those Afghan children, who were in the house with Mullah Wazir, who attacked aid workers. You can regret a mistake.

Do let me know when al Qaeda or Hamas expresses regret for what they do. They did it on purpose, you see.

As another example, if you believe that killing a child who is near the military target of a bomb is morally equivalent to a terrorist sighting a rifle on the forehead of a child in her bedroom and blowing her brains across the crayon decorations on the wall, I have nowhere else to go with this argument.