Chinese food is like a chameleon. It gets adapted very significantly to whatever local ingredients are available in a way many others don't, and also intentionally adjusted to local palates (I remember when the first Chinese restaurant in Oslo to serve "authentic" Sichuan cuisine in the late 90's -- the unimaginatively named Dinner in Stortingsgata for any Norwegians on here -- had to warn people to interpret the spice levels the way you would at an Indian restaurant, because most Norwegian Chinese restaurants before that made their food more bland to fit local preferences but the Indian restaurants didn't, so they became the benchmark)
New submission: The Ottomans invented the doner kebab, yet its fast-food variant served as a sandwich with sauce and extensive salad was invented by an ethnic Turk in Berlin. Berlin has, for historical reasons, a lot of ethnic Vietnamese inhabitants. Some of these have moved to Vietnam, taking with them the kebab, and inventing a variant called banh my doner kebab, which uses pork for the meat part, and adds sour vegetables and chili sauce.
Even then, mapo and kungpao often contain a lot of chilis, which came from the Americas via the Portuguese. So it's not untouched by American (continent) influence, just much earlier.
Yes, every city has Chinese restaurants with stylized Chinese food. It’s usually “Americanized”, but it can just as be as easily Thai-ized or Korean-ized or Japan-ised or whatever.