The American version of the Shiba and Japanese version seem to be very different in build and attitude.
This is a difference you might be perceiving due to the fact that the breed is fairly young in the U.S. We have only recently been getting imports that could be considered competitive on Japanese turf (the Japanese are notoriously hard to convince to part with their nicest specimens)- but the results have been amazing. In the early years people were importing animals that could not have been considered typey- they were mostly pets returning home with military families, and a far cry from breeding quality. In addition, the Japanese standard was interpreted incorrectly at first. The NIPPO standard is written in a poetic style that describes ALL the native Japanese breeds. It was assumed that one would be able to tell which "rules" applied to which breeds without any need of explanation. This is why you'll notice by doing some research that we have two white American Shiba champions. They will be the only ones in history, as we realized our mistake in interpreting the standard (white applies to Akitas and Kishu, but not Shibas), and rectified it. It is now a disqualification in American (as well as Japanese) show rings.
See if you can find some of the San Jo, Kumi, or HiTorq dogs. By using outstanding imports like Boku, Taro (top-producing Shiba stud of all time), LeeRoy (top Shiba all systems last year), Fumi, Chaka (JKCs top Shiba of all time, and a bitch at that), and Joni Morningstar's lovely import boys Kojirou and Musashi (both NIPPO champions), American programs have made huge strides.
As far as attitude- a lot of this is due to the differences in how our two countries show dogs. NIPPO presentation is very "hands off." The animals are required to stand without the help of bait, hand-stacking, or indeed *any* human assistance. They are expected to do so sometimes for upwards of 45 minutes without "breaking character." Tails may not drop, ears may not droop, and a lagging expression (too much panting), is severly penalized. In addition, most programs in Japan treat the majority of their stock as kennel dogs rather than family pets. There may be one favorite housedog, but the rest of the animals are kenneled for the majority of their lives, and thus are not very well socialized. It's very different than how we raise our puppies inside the house and underfoot.
Boku was a typical Japanese kennel dog. It took several months for my breeder to get him used to being pet at will, get his nails clipped (originally took three people to hold him down), and to allow examination by a judge (NIPPO judges do not put their hands on the dogs). He eventually became dependable enough to be trusted around most people, but she never let her guard down with him.
American show rings require a dog that is used to all of these things- that can deal with being surrounded by throngs of people and dogs, poked and prodded by judges, and come home and be a family pet at the end of the day.
Nevertheless, my bitch has a very typical Japanese temperament. She's not a lovey-dovey "oh cuddle me" kind of dog. She's extraordinarily independent, and would much prefer to do her own thing. People who pet or hug her are met with looks of disgust. She has the air of a displaced empress, LOL.
I'm curious as to whether or not you're really thinking of the differences between Japanese and American *Akitas?* Because there I would really be more inclined to agree with you. Japanese and American Akitas are arguably different breeds now. Japanese Akitas look more like "giant Shibas," where as American Akitas are larger in bone, and tend towards a more "bear-like" appearance. This difference is due to the fact that around WW2 Japanese Akitas were bred with GSDs, and several mastiff breeds in an attempt to make an effective fighting dog. These were the dogs American servicemen brought home with them. After the war, the Japanese realized that this was a far cry from the original hunting dog they had cherished. They designated Akitas as a national treasure of Japan, and began breeding them as they originally had.
Americans, in contrast, kept breeding the big-boned Akitas. This difference is so obvious, that several registries world-wide have elected to split the breed into Akitas (the original Japanese dogs), and Great Japanese Dogs (American Akitas). The AKC has yet to do this...and may never do so. A decision I take issue with.