I can give several reasons and tactical differences..
And you are neglecting the fact that Irag was attacked twice.
Prior to the first gulf war,, Saddam had the worlds 6th largest army.
He was the major power in the area,,supplied by both Russia and the US, however most of that was concentrated in Armor. He was a follower of Rommel. Which was fine for his country and terrain. He has some basic air power and limited Anti-Aircraft.. Mostly Tanks and Artillery. Gulf War 1,, we did massive bombing, Destroying his Anti-air and Air-force, much of the countries infrastructure and decimating his armor.
His troops were for the most part conscripted,,(not the most dedicated fighters).
The second war,,we targeted Command and control,, cut communications with the very limited resources he had.
Without command,,the conscripts had neither direction nor inclination to put up much fight.
Irag is quite different on several levels. Terrain being only one. They have a more diversified defense. They have been attacked several times and have concentrated on Defense rather than Offensive weapons. They have multi-layered Anti-Aircraft defense,, not relying on any ONE technology,, so that if one aspect is targeted,, they still have others.
They have a Robust Coastal Defense,, and a Homegrown Defense Industry..
And they are not conscripted,, they will be fighting for survival.
There is really NO comparison.
three weeks?? In three weeks,,The US will not even be a player, and the whole of the Middle east will be a massive war zone.
What an incredibly stupid thing to do.