Excellent questions. For quite a while, I have been asking myself if Saddam’s execution was justified.
Sadam Hussein was objectively one of the worst people on the planet and most certainly should have been held to account by the people of Iraq. That is the easy question to answer.
Just about everything else surrounding the US involvement in Iraq after we invaded is harder to answer objectively. From Debaathification, to seizing the presidential palace grounds and declaring it the US embassy (the largest embassy in the world), to letting Mookie Sadr live in 2006, to tolerating the Iranian influence and brutality against Sunni that al-Maliki brought, to bugging out when and how we did. All of it and so much more is questionable, but I think it's a given that once we went in (also itself a questionable act), Saddam had to get it in the end.