I hope you all will forgive my complicated title, but it was the briefest I could think of for discussing a rather complicated issue: how Chinese and Japanese cultures have been represented and transformed American popular culture.
The story has complications aplenty, starting with the fact that it involves one of the world's oldest cultures, one of its newest, both of them having grafted on parts of their culture onto a smaller, but no less powerful, and no less unique culture. The fact that the last one hundred or so years has seen tragic and violent military confrontation between them certainly makes the case even more complicated.
Japan and the United States are both currently democracies and free market economies, and are relatively socially open. China has a free market economy, and is rapidly gaining social , if not political, openness. Due to the fact that Japan has been politically open and tied to the Unites States longer, there has been more commercial availability of Japanese cultural items in the United States. This seems to have made Japanese culture more widely reported in American culture, although the impact of Japanese culture in the United States may be due to more than availability.
Although Japanese and Chinese culture both have their advocates, students of both would probably have to admit the factual point that Chinese culture is not only much older, but takes in a more diverse set of circumstances, religions, ethnicities, and other sundry viewpoints. Japanese culture is adopted more easily, perhaps, because it is either easier to adapt, or because it is intrinsically simple.
Some of the most widely and deeply adopted ideas from Japanese culture highlight minimalism, militarism, and absolutism (as examples of each: sushi, the ninja and bushido), ideas that may or may not be "authentic" to Japanese culture, but that are problematic as mimed cultural values. When a pluralistic society such as the United States develops a fascination with the quasi-mystical belief system of an isolated, feudal aristocracy, does it suggest an authentic appreciation for that culture, a sign that we may be rebelling against the confusion of our own culture, or it may be a way to "appreciate" another culture while actually degrading it into a one note caricature of itself.
Of course, this is a very narrow version of Japanese culture, and doesn't address certain other aspects of the American obsession with Japanese culture: the interest in cuteness, or high technology. It would be very hard to say if their is an essential element to the cultural exchange, whether it is an American interest in Japan as such, or just an interest in things that happen to also occur in that culture.
If an explanation of America's interest in Japanese culture is hard to finish, an explanation of America's interest in Chinese culture is hard to even start on. In part, this is because post-coldwar fears and stereotypes of China as a monolithic beast still persist, and because comparatively little of China's culture has reached the United States. I do feel that in some ways, Chinese culture is harder to digest because it does not have a single stereotype or image attached to it: Americans still would probably describe Germans and Italians (who they have enough real experience with to not need to depend on stereotypes) as "orderly" and "passionate", but even the crudest person would be hard put to decide on what negative stereotype to subscribe to the Chinese. The fascination with Japan may stem, in part, from the United States projecting a value that we think of ourselves as lacking (homogenity, conformism, group awareness) onto another culture. It would be hard to think of what element we would project onto the Chinese. This isn't our problem alone: Chinese culture has defined itself by conflicting values for thousands of years, and seems to have trouble ever finalizing their cultural canon. But the issue of what influence Chinese culture will have on America will probably have to be decided in a generation or two, when Chinese popular culture penetrates American as much as Japanese culture has.
In other words, very little has been decided here, although hopefully a discussion has been started. | 
