The U.S. is obviously playing the part of 1900-era Imperial Britain, but the growing power is China (playing the part of 1900-era America) and the resource holders are the Middle Eastern Arabian and Persian states. I would propose that as it develops, China's huge demand for external resources and her perhaps even less fluent approach to foreign policy will result in a war between the Arabs and China, or possibly between Europe and China over control of Arabia.

The current action in the Middle East is a sideshow compared to what will happen when a country openly tries to take the oil by force.

When considering the U.S., it is easy to forget that the New World still has a low enough population density and enough unexploited resources that both Noth and South America can run good economies in isolation. It's the Far East and Europe that have the problem of resource constraints.