For one, it wasn't just for biological weapons, nuclear and chemical were also suspected.
Links to terrorism was also a factor, no direct links to Al Queda, however one of Usama's puppets "Abu Massad Al-Zakawi" is inside and is actively fighting the US with his terror cells inside Iraq.
uhh, I also believe he(saddam) broke like 17 UN sanctions.
California running out, you say? Well just move to Alaska, or oil deep in the sea. Besides, I highly doubt the rate of oil consumption will make Cali dry anytime soon.
How long will this war take? 2-4 years, IMO. The enemy will fail, the insurgencies cannot maintain this rate of damage, the "smoke screen" the professional terrorist are useing is thinning, they can't hold on forever like this. Unlike Vietnam, they havn't a pool of tens of thousands of men to pump from.