Um, how about a bit more reality first? "Revenge?" Bush Jr could've had plenty of "revenge" by targeting Saddam specifically. Kinda like Bill Clinton did upon learning of the Iraqi assassination plot.
Nah, it was revenge. Some childish mano el mano horseshit. Bush II saw not overrunning Iraq as his father's greatest failure, the timidity that unwound his Presidency and lost his second term. It was unfinished family business.
The US led its coalition into Iraq for a number of reasons.
Lies and fabrications basically. Mobile chemical weapons labs, yellowcake uranium from Niger, fleets of drones capable of reaching America ready to spray chemical weapons, yadda yadda yadda. Imminent threat! Existential threat! Lies. Not exaggerations. Lies. Not mistakes. Lies.
First and foremost being the continued violations of the Ceasefire Agreement. The Iraqis had zero credibility in their claims of having disarmed themselves of their WMD. This, thanks to the years of subsequent UN investigations of Iraq which kept uncovering more and more WMD that the Iraqis swore they didn't have.
Funny how Bush II refused to let the Weapons Inspectors conclude their work. I guess he had a war to get on.
Which, after the invasion, it turned out they really didn't have it! Gosh!
Some of us were actually around for this crap.
Another reason why the US went into Iraq was to shift the focus of the "War on Terrorism" from having to fight it in a reactionary mode within America's own borders and the borders of the other Western countries to fighting it within the borders of an enemy's country.
Of course, the Saddam Hussein regime was absolutely hostile to Al Quaeda in a 'shoot on sight' and Iraq wasn't actually a source of Islamic terrorism.
And the US was already in Afghanistan, bombing craters full of rubble looking not so hard for Al Quaeda.
It's a lot better and easier to do so "over there" than in your own backyard.
Or to just pull bullshit out of your butt.
As far as that aspect went, it succeeded handsomely. Agree or disagree with how the US led coalition handled "winning the peace" in Iraq after having deposed Saddam, the US occupation of Iraq served as a magnet for jihadis and Islamist terrorists throughout the Middle East and it drew them there by the thousands.
That's a wonderful fairy tale, and I'm sure it's very heartwarming to the millions of innocent civilians, women and children whose homes that the US decided to turn into a charnel pit. But it doesn't actually hold up all that well.
The vast majority of the Iraqi insurgency was home grown. America created tens of thousands of new terrorists, guys who would go on to found ISIS, who would bring new blood to the Jihadi movement, who would go on to create new bloodbaths in Mail, Mauretania, Yemen, Libya, Syria, Somalia. People who launched campaigns of genocide and ethnic cleansing.
So America's gift that kept on giving, over and over. It's no wonder so many people around the world think Americans are assholes.
Were there foreign Jihadi's that came to Iraq? Yep, some. Mostly the local insurgents welcomed them with open arms, and stuck them in suicide vests.
That meant they came to fight on ground of America's choosing where the US could employ its military superiority to a far, far great extent than it would've been able to had the battles been taking place in New York, Los Angeles, London or Paris. Over time, this resulted in the elimination of thousands of extremists who were thus not destabilizing their home countries or taking their battles to the Western countries.
It still baffles me why Bush & Blair chose to make such a non-issue of all the WMD we did find in Iraq. In fact, the coalition forces were pretty active in downplaying it.
Oh yeah, and here it comes. 'America did find tons of WMD in Iraq! We just covered it all up, that's all!'