This article says 300k civilians died in the immediate wartime, more died in the aftermath. For example, see https://www.washingtonpost.com/world/2023/03/20/iraq-broken-...:
With little doubt, the United States broke Iraq. U.S. forces succeeded in the campaign to topple Iraqi dictator Saddam Hussein... But what followed turned into a debacle for U.S. grand strategy, and a traumatic nightmare for much of Iraqi society.
The war, driven by the hubris of the Bush administration and a supportive Washington establishment — as well as what has to be described at this point as a vengeful post-9/11 bloodlust that permeated American society — is now widely seen as a generational American mistake. ... According to Brown University’s Costs of War project, many of the 306,000 estimated deaths in the Iraq war were of civilians killed by “direct war related violence” between 2003 and 2019, a span of time that saw Iraq convulsed by waves of insurgencies and counterinsurgencies, and its cities ravaged by terrorist attacks and airstrikes.
The consensus now, even among formerly hawkish Republicans, is that the United States should never have invaded Iraq 20 years ago. ...
“Iraq quickly fell prey to chaos, conflict and instability, experienced an uncountable number of deaths and displacements, and the erosion of health, education and basic services,” wrote Iraqi academic Balsam Mustafa. “Behind the statistics, there are untold stories of agony and suffering. The structural and political violence would spill into social and domestic violence, affecting women and children. With every life lost, a whole family is shattered. From day one, the conditions were forming for the emergence of terrorist groups and militias.”
from https://en.wikipedia.org/wiki/Rationale_for_the_Iraq_War
* 9/11 members were known to be in Iraq (we ignored the significant Saudi presence in actuality for the 9/11 attack)
* In the days immediately following 9/11, the Bush administration national security team actively debated an invasion of Iraq.
* The false claims of weapons of mass destruction in Iraq
* "A study coauthored by the Center for Public Integrity found that in the two years after September 11, 2001, the president and top administration officials had made 935 false statements, in an orchestrated public relations campaign to galvanize public opinion for the war, and that the press was largely complicit in its uncritical coverage of the reasons adduced for going to war.[70][71] PBS commentator Bill Moyers had made similar points throughout the lead-up to the Iraq War, and prior to a national press conference on the Iraq War[72] Moyers correctly predicted "at least a dozen times during this press conference he [the President] will invoke 9/11 and al-Qaeda to justify a preemptive attack on a country that has not attacked America."
That is not true. I remember Bush’s address: https://georgewbush-whitehouse.archives.gov/infocus/iraq/new...
I would say that US military doctrine has successfully created the most peaceful era in human history as measured by mortality rate due to conflict, and a fundamental part of that is the willingness to confront adversaries with overwhelming force. The alternative is generations of tribal conflicts. Coming from a family with many war deaths over the past several hundred years, I’m thankful the violence ended with my generation.