More precise than my mental calculations, here are some statistics in Harper's Index style.
U.S. Daily oil consumption, million barrels: 18
Yearly consumption, million barrels: 6,570
Round number price of a barrel of oil: $100
Cost of U.S. oil consumption for on year: $657 billion
U.S. Defense Department budget, 2010: $663 billion
The last two numbers are surprisingly similar. Of course, that is pure coincidence based on the price of oil and current consumption. But it makes you wonder how much we could reduce the last number if we reduced the first number.