Good question ericy - here's some responses to consider.

"Would the United States work to reduce demand if China did nothing, for example? Or what if all nations agreed to reduce demand, but some only made half-hearted attempts?"

I think this could be done hand in hand with multilateral trade & security agreements. If a country did not participate or made meaningless gestures, the rest of the group would have to threaten to do something meaningful like increase trade tariffs or kick them out of whatever regional defense network they belong to. But the idea is that solidarity is paramount. If that's not possible, then it's back to laissez-faire market demand destruction - messy, inequitable, social upheaval - in other words, the perfect environment for dictators and demagogues. We need to have proactive leadership now to head off the more ominous scenarios later.

To fight the power of a cartel, you have to think like a union. We hang together or hang separately. Plus, by reducing your net consumption of oil you are improving your balance of trade, holding down inflation, which at these prices is a real risk.

Finally, if we did all of these things and were able to successfully bring the price down, would there not be a strong urge for people to try to backslide into old behaviors?

The idea is to start to put into place the societal behaviors that will reduce consumption in a more orderly and equitable way that maintain the social fabric. Some of these short term measures would be done on an "emergency basis" at first but they might gain popularity as they make people less dependent on oil and can be supplemented by more long term investments in efficiency in buildings and increases in gas mileage on newer cars.