This article is a great analysis of why Chavez wouldn't cut off oil supplies to the US. The author obviously has a better sense of the numbers and economics of why it would be stupid for Chavez to make good on his threat. But it doesn't take a rocket scientist to know that the US wouldn't miss their number 4 oil supplier (in the 10% ballpark I think?).
He makes an argument about becoming energy independent that makes some sense, but I would disagree with him slightly in this regard. The US needs to be energy independent from ALL foreign sources of oil, not just Venezuela. If we were energy independent, we would gain the economic and political advantage over those countries who now hold our economy by the purse strings.
Oil makes this country work, and we have become unashamedly dependent on it. Unfortunately, we're also sitting on billions of barrels of it ourselves that we won't tap because some nearly extinct wild life. Yet we have no problems buying oil from people who don't care about the environment, and are more than willing to take our money.
No one need look too far to see who the growing economic powers in this world are: Dubai helps prop up major financial institutions in the US, and so does China. Sure, both of these countries would be devastated if the US economy were to take a dive, but the fact that they can prop up companies to the tune of billions of dollars? Not such a good thing.
(Okay, China doesn't produce oil - yet - but we've become so dependent on their cheap products - thank you Wal-mart - that they have billions of dollars to do with as the wish.)