What's the deal with genocide?

Ignoring the fact the I titled my first blog Jerry Seinfeld-esque this is a very serious topic, genocide that is. Also, ignore the fact that I started this post last year and am only finishing/posting it now.
Last year I read "A Problem from Hell": American and the Age of Genocide by Samantha Powers. As I write this blog I am only about halfway through the book, but nonetheless I have already been able to see patterns develop with U.S. foreign policy, mainly when it comes to dealing with genocide. Put simply, the U.S. likes to not use the word genocide. One reason being that if the U.S. did deem something a genocide then it would have to get involved in some way, shape, or form to stop it.
From what I gathered from my reading is that the U.S. does not like to get involved 1) the thought of sending troops to stop a genocide does not bode well for public opinion and 2) usually if the U.S. would have decided to step in during a genocide it would somehow end up hurting itself. Examples of this can be seen during the Cold War period.
One specific example is the Kurdish genocide in Iraq. This genocide was enforced by Ali Hassan al-Majid, Saddam Hussein's cousin and secretary-general of the Northern Bureau. The reason for the genocide against the Kurds was because of a ongoing war with Iran. The certain Kurds were allied with Iran and were considered "rebels" in Iraq, therefore, Iraq justified removing the Kurdish "rebels" saying that they were trying to bring down the government. The problem was that the "rebels" that the Iraqis were removing were not only men but women and children and then systematically destroying villages. The whole Kurdish genocide is much more complicated than that.
The reason the U.S. did not want to get involved was because the U.S. did not like Iran, therefore, the U.S. supported the Iraqi government. The U.S. feared that if they spoke up that they would lose an ally in the war with Iran.
Now fast forward 20 years and we are faced with another genocide. This time it is happening in the Darfur region of Sudan. So far 400,000 have been killed and more than 2 million people have been displaced. Repeatedly the U.S. and the world community has said "never again" would a genocide occur. In reality, countries continue to turn a blind eye to these types of atrocities. This time the U.S. is afraid to act because the Sudanese government gives the U.S. "valuable" intelligence in the war on terror. If the U.S. were to stand up to the Sudanese government they may lose that support for the war on terror, therefore, the janjaweed militias and government forces are able to continue killing Darfuris.