We did not routinely kill surrenduring Germans or Italians. We did not round up every ethnic German and Italian living in the Eastern U.S. in 1942 and ship them off to concentration camps. We treated different enemies differently based only on their ethnic backgrounds.
I am sorry that you think that it is OK to treat different ethnic groups in different ways for the same acts, but that really is the essence of racism–you feel that it is OK to use another person;'s ethnic background to change your actions.
As barbaric as Japanese behavior often was–and it was–we had signed the various Geneva and Hague conventions that held us to a higher standard of behavior and we simply abandoned our principles because we considered one group of (Asian) enemies inferior to a different group of (European) enemies. The Germans had been killing Americans by torpedoing ships for months before Pearl Harbor, yet we did not routinely treat them in the same manner.
That you see no hatred of Japanese today is a function of several different events. One thing is time. A 21 year old in December, 1941 will turn 90, this year. People who grew up on Godzilla and Toyotas and Sony do not necessarily share the values of their predecessors. In the 1950s, movies such as Teahouse of the August Moon and Sayonara presented a slightly younger audience with a more sympathetic portrayal of the Japanese, (still using ethnic Europeans in heavy makeup to portray the important Japanese people, of course). There are dozens of ethnic Japanese appearing on TV and in movies, nowadays, so that viewers tend to see them simply as “people” rather than as buck-toothed, squinty-eyed vermin as they were typically portrayed during WWII. Following the war, when a lot of troops were stationed in Japan, and later when the U.S. used Japan as its base area for the Korean War, some of the racism abated as Yanks got to know the Japanese people, personally.
Another aspect is that overt hatred is rarely acceptable in society, these days, so, unless you personally encounter a person expressing hatred, you may not be aware of it. When Japanese cars were first drubbing Detroit cars in the market, there was a lot more freely expressed hatred floating around, particularly among workers, then in their late fifties or early sixties, who still harbored their WWII feelings. In fact, two idiots in Detroit murdered an ethnic Chinese man, (since they could not tell the difference between Japanese and Chinese), for “taking their jobs” and the fool of a judge, (of roughly the same age), who heard the trial wound up giving them slaps on the wrist because he could “understand” how they felt.
The fact that most of that racism has finally been put behind us says nothing about the amount and level of racism that occurred in the country during WWII.