An American reading about atrocities committed

Reading the Rape of Nanking is difficult for many reasons. One is the content, but the reason that's been most prevalent on my mind is the images of destruction and despair coming out of Japan in recent days. Iris Chang makes a strong case against the Japanese in her book, citing the psychology of its entire culture.
However unfair it sounds, reading the early chapters and introduction of this book, it's difficult not to hate the Japanese a little bit. As an American of German descent, however, WWII is a bit of a sore spot, as it is. It is impossible to discuss the Japanese without the bombing of Hiroshima and Nagasaki at the back of my mind. I feel somehow unjustified in judging.
Rachel Maddow tells me that once again, nuclear radiation is floating around Japan during this already tragic time. I am also reminded that during the quake in Haiti, Japan raised and donated a lot of money for the clean-up effort. I was impressed by their actions, and dismayed that donations for Japan have been "slow" and small.
Coming from a powerful country where atrocities against us are propagandized into action, it's difficult to imagine already being at war with an invading army when something of the magnitude of the Nanking Massacre occurs. While my own inexperience, and lack of private research on the Massacre gives me pause, Iris Chang's arguments seem sound, and her impassioned speech inspires. However, I suppose all arguments on such an 'obviously' one-sided issue encourage the same response.
My sympathy for the Japanese in 2011 gives me guilt for my judgment of them in 1937, and their inaction for reparations since. While I do not believe that we can judge an entire country, people, or culture on their attitude in one or a couple of events, I come from a culture that encourages (arguably) individual thought, and one where up to 49% of the population can disagree with the course our country is taking. The minority can be as vocal about their views as they please, without (in theory) stepping on the 'liberties of others.' Based on the writings of Iris Chang and basic research into Samurai culture, and a brief introduction into the history of Japan, our cultures do not appear parallel. Which again gives me pause. How much can a Westerner, with a Western education, truly make informed, intelligent decisions about an Eastern culture?
To follow it up, here's some links to charities doing work for Japan,:
UNICEF
American Red Cross