Mass Murder and Genocide

What's the difference between massacres and genocide? Granted, genocide seems more organized and systematic compared to massacres; but murder is murder, no matter how you look at it. They are still the act of taking another's life. You can say that massacres are indiscriminate killing of people, and genocide would be the slaughtering of a certain group or groups of people... But the end result is still the same.
When people hear the word genocide, the first thing that they think is probably the Holocaust. Of course, the Holocaust was a horrendous atrocity; but it's only famous because we the people have made it so. We hardly mention the large-eradication of Native Americans during the 1800's when the newly formed United States began their expansion westward towards the Pacific Ocean. We barely talk about the millions of civilians murdered in the Laos or Cambodia during the Vietnam War. Are we so conceited as to sneer and point out other people's actions, but completely be ignorant of our own atrocities?
We make Hitler and the Germans out to be demons and madmen out to eradicate life, yet we glorify General Custer, who was dead set on the mass elimination of Native Americans just so the US can gain more land. We say the Nazis were monsters for killing Jews, yet we have killed more foreigners in history than the Nazis. We say Hitler was racist and hated Jews, but who has the history of discriminating nearly every race that was different from white. We're all horrified at the use of chlorine gas and other weapons in the death and concentration camps all over Germany, yet we're the ones who gave small pox infected blankets to Native Americans. Again, I will refer you to my previous post America: Land of Hypocrisy.
Yes, Hitler and his Nazis were wrong in trying to eradicate the Jewish just because they were different. Some people may not wish to admit it, but the first thing that comes to mind when they hear the words Germany or Nazi would be Hitler or the Holocaust. Again, everything depends on perception and interpretation. Hitler was racist to the Jews and we besmirch him for it. Whereas the United States has had a history of racism. Racism against the Africans (African Americans included) brought here against their will; Racism against the Chinese who came here for new opportunities; and racism against the Irish immigrants who came seeking new lives. Hell, we even had a freaking concentration camp for Japanese people back in World War II.
Me must be truly ignorant if all we do is look at other people's actions and problems; not bothering to turn around and view our own flaws and vices. If we count up the numerous atrocities the US has committed, the Holocaust pales in comparison.

I'm too tired and bored to type any more. I'll continue this later.