I don't think that's why. I doubt the Japanese give a f*** about American culture, but the people here are all on their nuts. And everyone keeps saying it's 'because their different and ordinary', I disagree again. United States is different, but I'm not talking about the people, I'm talking about the stuff. My question is why kids here love all their crap. If they were so different all of their cartoons would look the same. When I flip past Cartoon Network, I can't tell if it's DBZ, Yu-Gi-Oh, Naruto, Pokemon, Naruto, Inuyasha, DBZ, Naruto, Yu-Yu Hakusho, Naruto, Inuyasha. It all looks the same.
Actually, to tell you the truth, there is a lot of interest in in American pop culture in Japan. 
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In a lot of the original language versions of Japanese shows, there's a lot of English interspersed throughout because of this interest. Also, American super-heroes have a rather cult folowing amoung some of the population in Japan as well. (In a lot of ways, it's why the Marvel vs. Capcom franchise even exists.)
I know that's true. In an interview, the film director of Zeiram said that he wanted to make a horror action movie because he was inspired by The Terminator, since The Terminator could change forms and still fight. Although I think Zeiram (the monster) is a lot deadlier then the Terminator, in fact I know it is. In the movie, Zeiram is immortal, unless you destroy it's head. (Which nobody ever seems to realize that). In the first movie they chopped it's head off and in the second movie Zeiram's head was put on a robot, which it possessed (kind of like that female Terminator in the 3rd Terminator movie).
A lot of people believe that FF in Japan is more famous then it is in America, but I think that's an understatement. Dragonwarrior (or maybe it was Dragon Quest) is the most popular RPG series in Japan, and Final Fantasy is more famous in America then Star Wars (if not, then it's as famous).
Cinco de Mayo