A large fraction of the Chinese restaurants in the US are run by recent
immigrants from Fujian province. They tend to all have similar
suppliers and menus and serve the same generic watered down
Hunan-Cantonese food, but if you live in a city with a large
Chinese-American community like New York or San Francisco you'll have
other options. Avoid Chinatown restaurants, most of which are just
tourist traps with overpriced terrible food, and look for restaurants
in untouristed neighborhoods with large Chinese populations, like
Flushing in New York.

The "Chinese" restaurants in Europe are even worse. Many of them are
run by Vietnamese immigrants, and serve completely bland versions of
the eight or so most common Chinese dishes and often of Thai and
Vietnamese food as well. In London or Paris you have some options, but
the quality of Chinese food in most of Europe is dismal.