(Even as it is, with 14% of our oil coming from Saud-owned Arabia, a embargo would not bring us to our knees, though it wouldn't be good, but the loss of revenue could very easily bring the Saudis to their knees.)
In other words, regime change in Iraq means a sharply declining rationale for the US - Saudi "special relationship," without which Abdullah and all his kin are chopped liver.
I'm personally glad Dubya is meeting Abdullah at the Crawford Ranch, though the nasty devil doesn't deserve the honor. Crawford brings out the Texas in Bush, which is exactly the frame of mind he needs to be in for this meeting.
There is an interesting article on The Strategy Page today that talks about the domino effect that the Iraqi operation could have.