Traditional Chinese restaurant in the US. are Cantonese. Nobody, but Cantonese, can or does own and operate Cantonese restaurants. The specialty includes some hot spicy entrees. They have a lot of Cantonese techniques in it, however it is very salty by Asian measure, which pleases the All-American taste, and considered to be inferior to Cantonese over all. Seafood is not original since Szechwan is over one thousand miles from the nearest ocean.
Excessive salt is perfect for non-fresh fish at the old days.
Szechwan restaurants in the States are mostly owned and operated by Taiwanese or other non-Szechwanese, since there are not that many of them in the States. The specialties are beef and lamb, partially due to Muslim influence, rather than pork or chicken. The restaurant decor is typified with royal dark red color without a trace of natural light. Exiting the restaurant in broad daylight to the parking lot can be a blinding experience. Again, there are lots of Cantonese techniques.