Not to defend the invasion, but the difference between say Japan post WWII and Iraq is almost entirely internal. Blaming the invasion for those deaths is not unreasonable, but it’s glossing over a lot of context.
As external observers it’s easy to think of Iraq as a horrific civil war. Yet, it maintained positive population growth so that’s not what happened. It’s more accurate to consider things in terms of Mexican gangs and lack of social order than civil unrest.