> So long as there are still oil-fired powerstations and a plastics industry, I doubt OPEC would really be overly concerned. IIRC, transportation only accounts for 12% of oil use, globally.

The Middle East would still certainly be an economic power even with a chunk of its market ripped out. But I would wager the dependence would be more significantly lessened than by 12%, even if that is indeed the percentage of oil used by transportation. Without foreign oil sources, the United States has enough oil to last about 30 days before demand catches up to what we can supply ourselves. Plastic is darned important, but I see transportation being the most devastating thing to shut down suddenly: if you can't ship plastic anywhere, it hardly matters if you have a supply of it.