I've been told by a great many people that it was invented in America and wasn't a Chinese dish at all!
My sister who traveled several times to the mainland said she has never seen it on a menu there. You think that is possibly a slight against Taiwan?
I have never seen it in my life and Japanese Wikipedia says that like Chop Suey it is an Americanized dish.
In general Chinese food is wildly different depending on where you eat it; there was not much in common between local Chinese food I ate in Beijing, Sichuan, or Kuala Lumpur.
Look at Hainanese chicken rice. It was invented by Hainanese immigrants in Singapore, and the only place you'd ever find it in Beijing would be at a Singaporean restaurant. But it's basically an unmistakable evolution of a classic dish from Hainan province. A lot of Chinese cuisine in SE Asia is like that.
Regarding chop suey, in San Francisco Chinatown there's a Chinese restaurant, New Lun Ting, popular with older Chinese-Americans that sells a version of chop suey that is arguably an authentic Chinese-American dish. Some other restaurants in Chinatown also sell chop suey or something like that, but it was always easy to dismiss as something sold to attract tourists--originally in earnest to meet their tastes, now more as an ironic thing. But now I'm fairly confident it has deeper Chinese roots, and is less adulterated, than is commonly assumed.
The longer I live in San Francisco, and the more I eat in Asia (Mongolia, South Korea, Taipei, Shanghai, Hong Kong, and all over Malaysia and Singapore), the more I realize how nuanced, complex, and interrelated the origins and evolution of Asian food can be. And the more I understand my own subtle prejudice--white Americans, at least the more cosmopolitan ones, instinctively understand that nuance and complexity when it comes to European cuisine.
And like with European fare, not all Asian fare is bold and exotic. It's easy to dismiss chop suey as something invented for the palates of Americans because it seems so plain and cheap; and because it seems so undesirable compared to common "authentic" Chinese dishes. But that's a subtle form of bias. There are plenty of boring American dishes, for example, that are completely unlike hamburgers, hot dogs, or BBQ and that foreigner would think couldn't possibly be "authentic" American.
I think mainland Chinese culture is much like American culture--relatively isolated and inward looking in practice, even if superficially outward looking. In both cases by the time some foreign influence seeps through the culture it's thoroughly transformed and unrecognizable. And nobody really cares because both are already intensely rich universes until themselves.
But maybe we're just making too much of your anecdote.