To directly answer your question, it may have been the case the known world oil supplies would have been depleted if the global per capita oil use matched the US. However, global oil supply far outstrips what are called proven reserves. For instance, 1970 estimates did not include oil shale, of which there is enough to match Saudi resources.
Fundamentally, yes, providing enough energy so that everyone could enjoy our standard of living is the largest engineering problem in the world today. Ultimately, the energy will have to be solar. geothermal is the only energy source we use that did not originate from the sun. To have a sustained energy supply, we cannot use more per year than what comes from the sun.
This is great news. Earth receives more energy from the sun in an hour than humanity currently uses in a year. The problem is to develop a capture method for this energy.
Remember also that every living creature relies on the sun's energy, and we can't monopolize it without mass extinctions. Ideally, we would have solar energy collection systems on all of our buildings and roads, and not ever on some kind of solar farm.
And that's the biggest problem facing the world today: overpopulation, leading to reduced habitat for other life forms. Energy is a comparably easy problem to solve.
Anyway, that's my opinion.
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"What if you just eat vegetarians?"-neonreaper
"^ You are what you eat. ^_~"-Koiji