What fraction of America’s $4+ gallon gasoline is due to the war in Iraq?

Earlier today, someone asserted that well over half (or more than $2) of America’s $4.10 gallon of gas is due to the war. Another person asked “Is that right?” And, after pulling out some hair from my head, my response was both short and then long.

The short: Two dollars a gallon is, perhaps, as good a swag as anyone’s. I think. The long? Well it’s more complicated.