The US is concerned about oil supplies everywhere in the world, because the US economy is driven by oil prices and the US net oil self sufficiency (though it's not self-sufficient in the oil it actually uses) has only slight bearing on this, since prices are driven by global market conditions.
Which is not to say that US interest in oil as the reason for the events at issue is a reasonable, evidence-supported belief.
Isn't it true the majority of oil used in the US is from the US now? We fell off in the 90s and 00s but I believe we are now amongst top producers again. I'm not happy about increased fossil fuel production but at least it takes some power from much less desirable hands like Saudis, Iran, Brazil, Venezuela, etc.
Which is not to say that US interest in oil as the reason for the events at issue is a reasonable, evidence-supported belief.