I can answer this as my great-grandfather was deployed to Shanghai and later Tokyo during the occupation and while he died in 1978, I have his journal and letters he wrote home to his wife, my great-grandmother.

He didn't particularly hate Japan, in his writings, in fact he was very interested and mystified by Buddhism, Shinto and many other aspects. However, he wrote that his CO had a penchant for drawing bucked tooth, toothbrush stached head with the cone straw hats and shooting at them when he was drunk.

However, he also wrote of the stories and rumours of Japanese torture methods and was bothered that Showa, the emperor, allowed them to do so.

Ultimately, reading his accounts of the Japanese along with some historical accounts of the occupation as well as the historical fiction novel An Artist of the Floating World, which details the shame a propaganda artist has in post-war Japan, along with watching his culture, family all change as the Western influence grows and details in one chapter the arrest of one of his colleagues for war crimes by the American occupiers - the colleague committed suicide in his cell out of guilt and dishonour. And while it's a fictional novel, Kazuo Ishiguro did base them on his own personal experiences but some details were likely manufactured for the sake of narration.

This was pretty common throughout the 1950s, but in the 1960s, Japanese cars began to be exported en masse into the US, Toyota entering the US in 1957 with the Crown and Corona, 1960 for Honda, and 1970 for Mazda. All of them were successful through the 1970s due to the US automakers being slow on the uptake of smaller more efficient cars compared to the landboats of the 1950s to the early 1970s.

As for anime, Osamu Tezuka's Mighty Atom/Astro Boy is the first anime that really was widely acclaimed in the Western world, it aired in Japan from 1963 to 1966 and in syndication the US from 1963-1975. Tezuka was not particularly pleased with the changes, but it did give Americans the first taste of anime. This was followed by Mach GoGoGo/Speed Racer which was aired in Japan from 1967-1968 and in the US from late 1967 to the mid-1970s, in syndication.

So this all comes down to three things: Our great grandparents and grandparents grew up with anti-Japanese sentiment, but as Japanese TV came to us in the 1960s and 1970s, the Japanese government passed reforms under the American occupation, the popularity of Japanese anime, Japanese cars as well as other Japanese goods has made it so that racism against Japan has softened significantly especially for people our parents age and our age as our parents watched Speed Racer and Astro Boy and Mobile Suit Gundam, and people my age grew up watching Pokemon, Dragon Ball Z and FLCL. That's also in addition to the blunders of big auto industry giants like GM and Chrysler in the 1970s and 1980s that caused Toyota, Honda and Mazda, as well as Nissan and Subaru to swoop in and offer cars that were simply better quality than what GM and Chrysler were offering to money conscious families. And finally you can't go without seeing big Japanese names like Yamaha, NEC, Nintendo, Sony, Nikon, Ricoh, and Panasonic in everything from computers to musical instruments, to video games, to motorcycle engines and from TVs to DVD players and appliances.

Sources

Osamu Tezuka - Anime Academy Website

Schodt, Frederik L. "Introduction." Astro Boy Volume 1 (Comic by Osamu Tezuka). Dark Horse Comics and Studio Proteus.

Japan Times "'Americanizing' a cartoon classic"

Frank B. Tipton, Asian Firms: History, Institutions and Management

Honda Motor Company Limited -- Company History. FundingUniverse LLC.

Toyota's 50th Anniversary in America - Toyopet

Russell, E. (2001). War and Nature: Fighting Humans and Insects with Chemicals from World War I to Silent Spring. Cambridge University Press