Belly dancing is Arab/Islamic and is just not part of Indian culture (it used to be when the Muslims rules but it's not something we consider Indian anymore)
Buuuuut Japanese restaurants in the States tend to be exceedingly Oriental in design, and probably don't look like that in Japan. It's probably to add to the atmosphere, but they just got their cultures mixed up.
It happens, and Japan isn't known for its cultural sensitivity at any rate