I understand that the Holocaust is a main focus when talking about genocide because of the fact that over 1 million were slaughtered but I do not understand why things like the Rape of Nanking are not as widely talked about. I do not remember learning much, if anything, about the extent of their crimes in grade school. In the case of Nanking, more than 200,000 people were murdered in a 3 month span and thousands raped. So why is it not really talked about in America? Is it due to the fact that China is a Communist country and therefore shouldn't be painted in a sympathetic light?
You mention in your post that you went to an American school. As American educational curriculum is more centered around Europe than Asia, it is likely that any studies of WW2 would be more involved with war crimes in Europe than war crimes in Asia.
As for why that is, the US simply did not have as many forces fighting in mainland China as they did fighting in the Pacific or in Europe. So, aside from such atrocities as those occurring within Southeast Asian POW camps, war crimes in China just aren't as relevant to the American education.
However, that being said, Japanese war crimes in Asia are still very much remembered by China, the Koreas, Singapore, and essentially every nation in between. These tensions are still serve as a major source of hatred and distrust between many mainland Asians and the Japanese, at least among the older generations.