Like it or not, the political situation in America is different than with the Gulf War. They didn't have the TIME to assemble the overwhelming force to nail them in a clean sweep. (They still haven't take the time, in my opinion). There's a large segment in America that wants action 'now'. Waiting even 3 months is too long for them ("we've been attacked damn it", they say).
It took, what, 6 months to go from Desert Shield to Desert Storm? There's a huge logistics effort to move thousands of tanks, troops, helicopters and planes...not to mention food, hospitals, etc.
We're attacking in less than 30 days.