Would Iraq still have same image in US as OTL. OTL constant flying and bombing, not to mention occasional increased campaigns kept Iraq in the news and in people's minds constantly. Plus it created an impression of unfinished business, "we failed to finish the job in 1991 so now we are stuck with this" making it easier to sell 03 invasion.
If there are no NFZ US would likely draw down it's presence. OK, USN would still have a carrier in Gulf but if there is less presence in Saudi or if there is none and forces needed to "keep an eye on Iraq" are shifted to Turkey how does that effect Al Qaida? Sure, OBL had problems with Saudis inviting US in but if US leaves after the war his essage might just fizzle out.