It wasn’t about Saddam. No more than WWII in Europe was about Hitler.
It was about shattering the model of allowing as legitimate some ancient rule in the 21st century.
And, if not us, who? What were we going to do, have Gulf War 3 in a decade? Do what Wilson did when he left the German military/political order still intact, and then WWII another generation, under worse terms had to bleed white Europe again to finish what Wilson willfully and knowing left undone?
Further, as a national expression, most Americans do think it was worth it. There were no strikes, Congress well funded the war, there was hardly a desertion, moral stayed good, and even the Obama administration continues Bush policies.
If our policy is/was to invade every country with a despotic leader why did we quit?