Wikipedia confronts standard folk wisdom:

Chop suey is widely believed to have been invented in America by Chinese Americans, but the anthropologist E.N. Anderson concludes that the dish is based on tsap seui ("miscellaneous leftovers”), common in Taishan (Toisan), a county in Guangdong Province, the home of many early Chinese immigrants to the U.S.

This "became the infamous ‘chop suey’ of third-string Chinese restaurants in the western world, but it began life as a good if humble dish among the specialist vegetable farmers of the area. At the end of the day, they would stir-fry the small shoots, thinnings, and unsold vegetables—up to ten species in a dish.

There are many versions of its origins, all specious.

I've never had it.