Take Cantonese (or heck, Teochew or Hakka). You really think this language is reasonably mutually intelligible with Mandarin? Or Shanghainese?
I'm a (non-native, formerly fluent but now pretty poor) Cantonese speaker and I'd describe the difference between Cantonese and Mandarin as roughly the difference between Portuguese and Romanian. Sure, they're both romance languages, and maybe with a lot of work and hand-waving and drawing characters on your hands with your fingers you can get your point across to someone who speaks the other language, but in no way would I call them mutually intelligible, even by talking "slower".
Cantonese and Mandarin have very different pronunciation, vocabulary, and even grammar for common cases. In fact there are extremely common words in Cantonese for which there is no modern chinese character: instead roman words or even single letters (like "D") are substituted in comic strips etc. So you can't even write them down in Chinese for a Mandarin speaker to puzzle through with a dictionary.
I'd say that your perception of these things as "western centric" -- they are not at all -- strikes me as very "northern Chinese centric" view of China. :-)
It's not necessarily a northern Chinese centric view of China as it is a Mandarin (as in the language family) view of China. The vast majority of Chinese dialects in a large band from Heilongjiang to Sichuan (and a bit out to Qinghai and Xinjiang) are more or less mutually intelligible. That mutual intelligibility drops off very quickly outside of that band. In particular a lot of Southeast dialects (Yue, Wu, Min, etc.) fall outside of that zone. But it covers the majority of Chinese speakers. (However, I disagree with the original claim that a Sichuanese speaker could understand Shanghainese).
See e.g. this video: https://www.youtube.com/watch?v=Ps7_NnkL-oM where for almost the entire video a couple is explaining words in their respective dialects (Sichuanese and Hunanese) to one another in their own dialect (i.e. not using Standard Mandarin at all in their explanations). The first half of the entire exchange is fluent and understandable by both people and also a Standard Mandarin audience. Only in the second half when they intentionally start quizzing each other on words they know will be tough for the other person and without additional context do they run into trouble (and occasionally resort to Mandarin).
Heh, this is the perfect place for me to jump in with some movie trivia.
Have you ever watched either Ip Man or "The Bridge" (Danish/Swedish cop show)?
In Ip Man, there's a gang of Mandarin speakers who show up in Ip Man's Cantonese world. They somehow are able to speak to each other, and I find it unlikely. Perhaps it's because my Cantonese is mediocre. But it just doesn't sound like you could have a casual conversation across the languages.
A similar thing happens in The Bridge. There's two cops solving a crime on the bridge connecting Denmark with Sweden, and they just talk to each other in their own languages. My guess is most people who didn't study the other language would not know all the slang, as importantly the simple expressions. Though I guess it could be learned easily; I can read a Swedish newspaper, just not process it fast enough to have a fast conversation with a colleague.
Similarly with German and Swiss German. Something about the way the sounds are different makes processing the other one a bit slow if you're not used to it.
> In Ip Man, there's a gang of Mandarin speakers who show up in Ip Man's Cantonese world. They somehow are able to speak to each other, and I find it unlikely. Perhaps it's because my Cantonese is mediocre. But it just doesn't sound like you could have a casual conversation across the languages.
So the mixed Mandarin / Cantonese conversations actually do happen. My wife's family are all native Cantonese speakers, but her uncle married into the family from another part of China. He understands Cantonese perfectly but is more comfortable speaking Mandarin; and everyone else understands Mandarin to various degrees but prefer to speak in Cantonese. So he just speaks Mandarin while everyone else sticks to Cantonese; and it's quite a fluid back-and-forth.
That said, for that to happen so naturally the way it does in the Ip Man movies is really unrealistic. First of all, Mandarin wasn't as well-known in Guangdong in the 1930's as it is now; and there's no way someone from another part of China could just show up and magically understand Cantonese: It would take at least a few months of immersion to be able to "listen" fluidly enough to have that sort of a mixed conversation.
Even more unrealistic is Ip Man 4, where he shows up in San Fransisco, and starts talking in Cantonese to people who have immigrated from Beijing -- including one of the character's 12-year-old daughter who grew up in San Fransisco. Yeah, that's not going to happen.
That's kinda interesting that he can do that. With a bit of recent Mandarin schooling I can see the langauges are quite similar, but as a kid whenever we had a Mandarin speaker visiting I was baffled. Same thing happened when I learned German, as soon as I learned the initial things like the pronouns everything clicked.
It's probably the case that all the often used words that you use in everyday life have changed, but once you get over the barrier there's a pretty smooth learning zone.
Just to be clear, her uncle has now lived in HK for several decades; I'm sure there was a several-month learning curve being able to understand Cantonese. It's not like Hindi and Urdu, where (I'm told) people with no previous exposure to the other language can communicate pretty readily.
But there are a huge number of words which are simply pronounced a bit differently; and the differences in pronunciation have a lot of predictable patterns. So once you're familiar with these patterns, suddenly a Mandarin speaker can understand a huge amount of Cantonese when spoken in context.
I'm a (non-native, formerly fluent but now pretty poor) Cantonese speaker and I'd describe the difference between Cantonese and Mandarin as roughly the difference between Portuguese and Romanian. Sure, they're both romance languages, and maybe with a lot of work and hand-waving and drawing characters on your hands with your fingers you can get your point across to someone who speaks the other language, but in no way would I call them mutually intelligible, even by talking "slower".
Cantonese and Mandarin have very different pronunciation, vocabulary, and even grammar for common cases. In fact there are extremely common words in Cantonese for which there is no modern chinese character: instead roman words or even single letters (like "D") are substituted in comic strips etc. So you can't even write them down in Chinese for a Mandarin speaker to puzzle through with a dictionary.
I'd say that your perception of these things as "western centric" -- they are not at all -- strikes me as very "northern Chinese centric" view of China. :-)