hypothetically, if US troops had found warehouses full of WMD shortly after invading Iraq, would it have mattered? They still would have faced the insurgency which killed roughly 5k soldiers and injured tens of thousands.
		
		
	 
So lets ignore the facts that Iraq chemical and biological warfare programs were effectively neutered (complete with Intelligence reports that stated as such) prior to Bush and co gunning for Hussein
Let's look at several scenarios. Each unique and has very important differences.
1. Iraq was actively producing, storing and maintaining chemical and biological weapons under the noses of everyone
Nope...no difference. 
2. Iraq  was actively storing and maintaining chemical and biological weapons under the noses of everyone
Nope..no difference.
3. Iraq  was actively storing chemical and biological weapons under the noses of everyone
Nope..no difference.
4. Iraq, due to administrative clusterfuck of Hussein's regime had unaccounted for stockpiles hidden away under the nose of watchdogs and unknown to Iraqi's. (the II don't know what that box is for but I'm not reporting it because Baathist will shoot me for being incompetent if I report it after so many years)
Nope no difference. 
5. Small stockpile buried years ago during Dessert Storm and follow up inspections, not maintained and pretty much useless from military value are unearthed after years in some field. the people that buried it dead or in prison for years.
Nope...no difference.
Think Tanks boys used chemical weapons as a boogey man to scare up support. It doesn't matter what they had. Wouldn't matter if we found nuclear weapons that rained mini Hitlers on the world. We would still have the same clusterfuck we have today.
Military operations against the Iraqi government had been ongoing since 1991.
Cheney and Rumsfeld  felt we should stop beating around the Bush and just get it over with. 
Instead of useless containment nonsense and the cost associated with it, they said
"We are a gatdamn superpower and we should show this little weasel whose boss so that the whole world knows we have a huge e-penis"
In their defense, what else were we supposed to do? Another decade of sanctions, enforcing air superiority,  inspections and attacking military sites while Hussein stayed in power? 
Not many graceful options left and it was getting t othe point of shit or get off the pot.
The problem was that the entire thing was planned by idiots who live in a Republican think tank bubble. 
Winning a war against some shitsville state that spent a decade under sanctions and military action from the worlds leading super power, a shitsville state that just prior to being on our shitlist came out of another long conflict with its Neighbor, is easy.
The idiots in the Bush administration thought 0 percent of what happens afterword. Something that they were warned of big time before the invasion.