For most of the twentieth century, Chinese restaurant food outside China was remarkably uniform in any given country — a specific adapted menu, repeated everywhere, bearing limited resemblance to how people actually eat in China.
That's changed substantially in the last two decades, and the reasons are worth understanding because they apply to other cuisines too.
Why the old menu existed
Several factors produced it.
Migration patterns. Early Chinese migration to many countries came disproportionately from specific southern regions, particularly Guangdong. The food that travelled was that regional cuisine, further adapted.
Ingredient availability. Many ingredients were simply unobtainable. Cooks substituted what was available, and the substitutions became the dish.
Audience adaptation. Restaurants serving a local clientele adapted to local palates — sweeter, less spicy, less use of unfamiliar textures and ingredients.
Economic pressure. Restaurants competing on price standardised around dishes that were cheap to produce and reliably popular.
The result was a coherent cuisine in its own right — one that developed in the diaspora and belongs to it — but which was frequently mistaken for Chinese food generally.
What changed
Different migration. More recent migration has come from a much wider range of regions, bringing cooks and consumers from provinces whose food had no presence abroad. Restaurants opened to serve those communities, cooking what those communities eat.
Students. Large numbers of students from across China created concentrated demand near universities for food from home, which is why so many regional restaurants cluster around campuses.
Supply chains. Ingredients that were unobtainable are now imported routinely. Sichuan peppercorns, specific chilli varieties, regional vinegars, preserved vegetables. Without them, regional cooking was impossible.
Information. Diners who read about regional cuisines arrive knowing what to order, which supports restaurants offering it.
What's actually different between regions
A brief and inadequate survey, since this covers an enormous area.
Sichuan. Known for the combination of chilli heat and the numbing tingle of Sichuan pepper, a sensation with no equivalent elsewhere. Also fermented broad bean paste, pickled vegetables and a great deal of complexity beyond heat.
Hunan. Also chilli-forward, and drier and more sharply spicy, using more fresh and pickled chillies and less numbing pepper.
Cantonese. Emphasis on freshness and precise technique, lighter seasoning, steaming, and the ability to taste the primary ingredient. The tradition behind dim sum.
Jiangnan region. Sweeter, with heavy use of rice wine, soy and sugar, and dishes with a glossy braised character.
Northern and northwestern cooking. Wheat rather than rice as the staple. Noodles, dumplings, breads. Lamb prominent, and in the northwest, cumin and influences from Central Asia.
Yunnan. Enormously varied, with mushrooms, fresh herbs, fermented ingredients, and influences from neighbouring Southeast Asia.
How to find and order
Practical suggestions.
Restaurants specialising in one region generally do it better than those offering everything. A menu covering Sichuan, Cantonese and northern dishes is unlikely to excel at any.
Look at what other diners are eating, particularly if the restaurant is serving a community from that region.
Ask what the kitchen is known for. Staff generally know and will say.
Where a separate menu exists in Chinese, it frequently contains dishes not on the translated one. Asking about it is entirely reasonable and usually welcomed.
And order across categories — something cold, something braised, something stir-fried, a vegetable, a staple. Chinese meals are structured around contrast between dishes rather than around a single main course, and ordering three similar things misses the point.
Cooking it at home
Two things matter more than technique.
Ingredients. Regional cooking depends on specific fermented and preserved products that cannot be substituted. Doubanjiang for Sichuan cooking, Shaoxing wine, black vinegar, specific soy sauces. These are now widely available and they're the difference between the real thing and an approximation.
Heat. Stir-frying properly requires more heat than domestic hobs provide. Mitigations: cook in small batches, get the pan properly hot before anything goes in, have everything prepared and to hand, and accept that some dishes won't quite work at home.
Braises, steamed dishes, cold dishes and noodle soups translate to home kitchens considerably better than high-heat wok cooking, and they're a better place to start.
The same pattern elsewhere
What has happened with Chinese food is not unique, and recognising the pattern is useful.
The same sequence has played out with Indian food in Britain, with Mexican food in parts of the United States, with Thai and Vietnamese food in several countries — an initial adapted version establishing itself widely, followed decades later by regional specificity as migration diversified and ingredients became available.
The adapted version is generally treated as inauthentic once the regional cooking arrives, which is a bit unfair. Those cuisines were created by real people under real constraints, they have their own histories, and some of the dishes are genuinely good.
The reasonable position is that both exist, they are different things, and neither needs to displace the other. What is worth resisting is the assumption that the first thing to arrive represents the whole of a cuisine.