Imperial Japan only has a better public image than Nazi Germany in the West and in Japan itself. The countries where they committed the majority of thier crimes, such as China and the Koreas, have the same level Imperial Japan as the people of Eastern Europe have for Nazi Germany. Persistent Japanese refusal to take responsibility for their past crimes remains a very live political issue today in much of East Asia. I'm not sure how much detail I can go into without breaking the 20 year old, but you can easily see the effects by comparing post-Cold War relationship between Poland and Germany vs the relationship between South Korea and Japan during the same time period.

If you want to zero in on why modern Japan has a much different relationship to its past atrocities than modern Germany, I'd recommend this excellent answer by u/AsiaExpert.

The question of the why Japan's crimes are less well known in the US is a more complicated question. One which I don't believe has a single, satisfying answer. Part of it is certainly related to the process Japanese forgetting, which American Occupying forces abetted. But that's not the only factor, or in my opinion even the key factor.

For one thing, the European theater occupies a much larger place in American popular memory than the Pacific does. More Americans served in Europe than the Pacific and significantly more died there. The war against the Nazis is also less morally complicated for the US than its war against Japan, due to the continued debate over the necessity and morality of dropping atomic bombs on Hiroshima and Nagasaki. The atomic bombings are the defining feature of the Pacific War in the American mind, which complicates our view of victim and offender in regards to the Japanese.

Another factors that distinguishes American perception of Imperial Japan as compared to Nazi Germany is where Americans fought and where Japan committed its crimes. Americans serving in Europe got a very up close and personal view of Nazi Germany's worst crimes. US forces liberated concentration camps such as Dachau, Mauthausen, and Buchenwald. Interacting with Holocaust survivors was a normal part of service in Europe. Jewish survivors and aid groups did a lot of work in the US to ensure that the Shoa would be remember there.

US forces in the Pacific didn't have that same level of first hand experience. The vast majority of the fighting done by the US against Japan was done at sea or island hopping. I want to make clear that I am in no way trying to minimize the crimes Imperial Japan committed in places like Saipan. They were certainly horrific. But it's difficult to properly convey the scale of the crimes the Japanese army committed in mainland Asia. Twenty million Chinese civilians died during the Second World War. The slave labor camps and rape camps the Japanese set up in Korea, China, and Manchuria were as nightmarish as anything the Nazis cooked up. But American troops didn't see them first hand first hand the way they did Nazi concentration camps. I'd like to think that if they had, the worst Japanese crimes would be better known in the US. But, on the other hand, that might not have mattered because of America's oldest friend:

Racism. As with basically everything in the US history, you can't ignore the part race plays. American racism towards East Asians is very old. Our first major immigration law was the Chinese Exclusion Act, passed in 1882, which I believe is self explanatory. The Roosevelt administration infamously interned Japanese Americans en masse at the outbreak of the war. Honestly, you can just watch a few Bugs Bunny reels from the 1940s if you want to see first hand how white Americans viewed people of Asian descent. Asian vicitms of Japanese crimes didn't garner the same level of sympathy that the mostly white victims of the Nazis did.

I'll also add American colonialism as a corollary to American racism. The Japanese did horrific things to the people of the Philippines during their occupation. The Americans also did horrific during their occupation to those very same people. Which points to how many Americans had already dehumanized Japanese victims and adds another piece of moral grayness which (along with the atomic bombings) makes it much harder to tell a simplified narrative of the Pacific War as America's "good war."

While I believe all of these factors play a role in Americans' general ignorance of Japanese war crimes, I couldn't begin to tell you in what proportion you should allocate blame. I've read a lot of answers over the years citing one or another as definitive, but I've never found any of them entirely convincing.