Afghanistan and Pakistan are
Afghanistan and Pakistan are a key route to pipelines to the Gulf and Near Asia. Owning Syria would give an open flight path from three directions into Iran, notably from the Mediterranean near Israel, and would mean Jordan would be surrounded as well.
Less than 20% (closer to 15%) of the oil used in the United States actually comes from the Middle East. The EIA says that we import about 45% of our oil and more than half of that import is from this hemisphere - mostly Canada and Mexico. When you factor in all of the petroleum-related products imported and exported, the U.S. is actually a net exporter of oil.
The wars in the Gulf have little to do with securing oil for ourselves or our national security and a lot more to do with securing the pipelines for the western profiteers.