It’s like how 95% of the “Chinese” places you go probably have General Tsaos chicken. It is not Chinese. Invented in Murica for Muricans. Deep fried sushi is the same. The restaurants in the US offer it because others offer it and the American pallet likes it.

You would be promptly murdered in Japan for asking for such a dish. Probably being the reason the restaurant puts up a “no foreigners allowed” sign from then on, which is actually common.

Same county that loves Tempura, but deep fried sushi is sacrilegious. Go figure.