We only got involved in the conflict because of our oil interests. Look at other parts of the world where there has been widespread human rights abuses and atrocities perpetrated by the government- Darfur, unstable governments in Africa etc. we never got involved because there was not a consumable good that the U.S. needed.
The US gets 2.77% of it's oil from Iraq. In 2001 that number was 4.5%, and it dropped significantly when we went to war with them. The US pumps more than a quarter of its own oil. If the entire Iraq war was about oil, then why do we import next to no oil from Iraq?
Contrary to some peoples belief there was WMDS in the region. Not nukes, but rather chemical gas. However, once we arrived we found evidence that the gas had been there, but was movec shortly before the troops arrival. This gas would later turn up in the gas attacks that were used in Syria.
The US, like all other countries, must concern itself with access to natural resources like oil. However, that does not mean that oil is the US's only motivation in Iraq. The US has an interest in broad regional stability in the Middle East, for reasons beyond simply access to oil. Large regional conflicts directly imperil US security. Therefore, a conflict like is currently brewing in Iraq is concerning for the US in ways unrelated to oil.
No, if it weren't for oil, the U.S. government would not care about Iraq. We have a long precedent of only caring about Iraq in order to lower our gas prices. That was our motivation for the Gulf War a generation ago. The U.S. government cares about its interests, not about a humanitarian crisis.