A war that was started on incorrect pretenses is not the same thing as terrorism. Among other things, the US did not deliberately target the Iraqi civilian population, and made their best efforts to avoid civilians being harmed. The US provided substantial reconstruction aid to Iraq to help undo the damage of the war afterward - more than $60 billion.
However, it's hard to avoid there being some undesired casualties in war, especially when the the fighters on the opposing side are using guerilla tactics and hiding within the civilian population, such as deliberately fighting, sniping, or using mortars from within what are otherwise civilian compounds, or even mosques, forcing the US to either ignore the attacks (unacceptable) or respond and attack mosques and civilian compounds.
All of our soldiers are unformed, with a flag, and follow rules of engagement that involve not attacking anyone except positively identified targets (i.e. observed holding weapons). Terrorist groups operating in the middle east wear no uniform and exploit our rules of engagement by attacking, dropping their weapons before the coalition can respond, then pretending to be civilians. Even though they're the only men-of-age in an area from which an attack just took place, since they stashed their weapons somewhere, the rules of engagement mean that our troops can't do much if they didn't observe a person holding a weapon.
Uniformed soldiers fighting other uniformed soldiers is different than terrorists that attack civilians or soldiers and then hide, pretending to be civilians.
The Iraq war was started on pretenses that we now know are false, but let's not conflate that with groups that deliberately target civilians (with suicide bombs in shopping centers), or conduct attacks even on military facilities and then pretend to be civilians when pursued for a counter-attack.