The maximum capacity of the Strategic Petroleum Reserve (SPR) is 700 million barrels. Presently it is less than 600 million barrels (it was drawn down to 540 MMBO late in the Clinton Presidency and is being charged now - a more precise figure may be available at the Energy Information Administration link I gave above).
If we were to lose all imports suddenly, and assuming the SPR were fully charged, it could take up the 55% slack in our daily consumption of just under 20 MMBO for two months. Assuming some state of national emergency were to be declared, and consumption restricted (and restrictions would likely fall on the general public as it would be foolhardy to cripple industry in a time of economic crisis), you might squeeze that out to three months.
That is nowhere near enough time to bring newly sought domestic production online, although it would definitely accelerate the drilling of inventory prospects. And, of course, drilling efficiency drops when the bum’s rush is on. Should the ANWR battle be won the day this happens, it will be a minimum of two years before that production feeds into the market. Same time frame for any other new exploration province. But, new production would appear from inventory drilling and rapidexpansion of efforts in currently exploitable areas, and as the price would rise, more and more economically marginal resources could be exploited.
So, there’d be some belt tightenin’, but the supply would be there, to some degree.
And, OPEC et al would take some hickies as well while the world market adjusted to the newly energy independent U.S.
That’s one scenario - if OPEC laid an embargo on us again, Mexico might well feel that it’s prime time to be pumping to el Norte; the calculations above do not explore that possibility.