Different dialects of Chinese you mean, and mandarin works well enough in most places as China also has a lot of transplants. You could love and work in Chengdu without without speaking sichuanese, for example.

In India, the unifying language is English, though it isn’t as widespread in India as mandarin is in China.

> Different dialects of Chinese you mean

No, the use of the term “dialect” is propaganda from the diversity-denying central government; describing Chinese languages as “dialects” is a gross abuse of the English word “dialect”, comparable to saying that French, Portuguese, and Romanian are all just dialects of Latin. “Chinese” consists of many mutually unintelligible languages (hundreds?), each of which has multiple dialects.

Mandarin works well enough as a lingua franca because (a) there has been a tremendous effort to force it on the population and suppress local culture (e.g. forcing children to speak it in school, force mass media to use it, etc.), and (b) there has been a massive internal migration in China so that a large proportion of the population is no longer living in their native land.

In some ways it is similar to the way young people from different European countries now speak English as a common language.

This analogy doesn't include the part where the written language is mutually intelligible due to thousands of years of imperial record-keeping.

Sichuanese is much more of a dialect than Cantonese. Even my sorry laowai Chinese can make some of it out. Cantonese and fujianese are about as far away from mandarin as dialects get, and they still are somewhat intelligible with manadarin and each other. The real different languages of China are like Tibetan, Mongolian, zhuang, Miao, Uighur, and a plethora of minority languages, but < 10% of the population speak them.

Mandarin gets you far for work or life in China in most Chinese cities. It stops working that great once you get to heavy minority areas outside big cities.

> Even my sorry laowai Chinese can make some of it out

In a similar way, as a not-great Spanish/French speaker, I can understand lots of Italian words and grammatical constructions, and often get the gist of random Italian quotations that pop up in books written in English.

Doesn’t make them the same language.

You are seriously overestimating how much Chengdu hua or Kunming hua differ from mandarin. Yes, they are crazy weird accents, but no, it’s not like a Spanish speaker picking out some Italian words, not even close. Same goes for dongbei hua or shandong hua, it only starts getting weird in south east China (Cantonese, fujian/min yu, kejia hua, etc...), and even then, those dialects are still Chinese with lots of nuances, not to mention they are similar to each other as well.

According to Wikipedia, Sichuanese shares <50% of its vocabulary with Beijing Mandarin. That is significantly further apart than French or Spanish to Italian. (Disclaimer: I know very little about the relation between Sichuanese and Beijing Mandarin, and would be happy to see better explained quantitative comparisons.)

Maybe you are underestimating how close Romance languages are.

In any event, I think everyone would agree that Sichuanese is much closer to Beijing Mandarin than other Chinese languages (like Xiang, Wu, Hakka, Min, etc. etc.).

Link?

Here: https://en.wikipedia.org/wiki/Varieties_of_Chinese

Officially sichuanese isn’t even considered another variety of Chinese (nor are any other western Chinese dialects). It’s even just called southwest mandarin: https://en.wikipedia.org/wiki/Southwestern_Mandarin

The page specifically for chengdu mandarin doesn’t mention anything about 50%...https://en.wikipedia.org/wiki/Chengdu-Chongqing_dialect