Americans did not dance for joy, unfurling national flags and toppling statues of leaders on 9/11. The terrorists did not liberate America from an oppressive dictator, who would crush any who dared suggest the thought of opposition.
When someone dies in an act of violence, how their death is perceived depends on why they died.
A soldier's immediate family will mourn, then resolve to honor their memory and the principles they were fighting for. The death of a soldier is treated with respect and reverence.
A civilian dying during a battle for the freedom of their own country; while not a combatant, they are accorded the same remembrance and respect as a soldier. It was inevitable that some should die during the liberation of their country, and the ones who eventually did die will be remembered as a symbol of their country's struggle. They will be thanked by the millions of Iraqis who live on, now free from the nightmare of the last three decades.
The civilians who died on 9/11, and the ones who died under Saddam's rule, died for little or no reason. A purposeless death is the most painful for family members, and stirs up desire for revenge. The word for it is murder. They were the actual target, and their death was the whim of a cruel madman. Their death did nothing for their country, and their relatives are robbed both of their family member in life, and any sense of purpose in their death.