If terrorists didn't kill thousands of Americans on 9/11, those wars don't happen, so you'd have to say 9/11 started it. Ironically, the world had less combat deaths worldwide than ever during those two wars (although this does a terrible job of capturing deaths caused by war, but not directly from combat): https://ourworldindata.org/war-and-peace
The 90s were relatively peaceful compared to the previous few decades, but we still had the Yugoslav Wars, Israeli-Palestine at times, the Gulf war, Rwanda.
The narrative to push the war on Iraq largely also revolved around "WMDs" while the legality of the war still remains debatable.
> Ironically, the world had less combat deaths worldwide than ever during those two wars
I wouldn't measure peace just by number of deaths, but even if we were to do so, it is also worth taking into account the increased security measures and the less freedom we have to prevent deaths.
sounds like the war shouldn't have happened, and the correct solution was not to do that