I wonder whether it makes sense to consider the east Asian languages (Chinese, Japanese, Korean, Vietnamese, and potentially others) as part of a sprachbund, like the European languages in standard average European
The CJKV languages have a long history of contact and a great deal of shared vocabulary borrowed from classical Chinese, but there are many similarities that go beyond vocabulary (and cannot possibly be due to genetic relationship)
For example:
Prominent use of classifiers (AKA counters, measure words)
An elaborate system of honorifics/politeness
At least partly Pro-drop
Use of Reduplication
simple tense structure; verbs that conjugate according to tense (if at all) but not subject. (Chinese formally has no tenses but sort of has a past tense via addition of -了)
Phonology: mostly CV syllable structure; few final consonants other than -n or -m. (And in general it seems speakers of CJKV don't have as strong of an accent when learning other CJKV languages versus foreigners from outside the region).
A system of single syllable grammatical particles.
Use of the possessive to form adjectives from nouns. For example in both Chinese and Japanese, "great hero" would literally translate to "greatness's hero".
Head-final in noun phrases.
Allowing the use of third person to refer to oneself or one's audience, in both formal and informal contexts. In the formal case, for example the utterance "I am here to serve your majesty" might be rendered as "the servant is here to serve the king" in Japanese or old-fashioned Chinese. In informal and colloquial situations, there are many times when one uses third person (especially with a nickname) in place of "I" or "you". Even in English when speaking to young children we use phrases like "Daddy is here!" but this practice is far more common in Chinese or Japanese and can be used among older kids or adults.
Rare use of third person pronouns. Japanese and Chinese have words for he/she (彼、彼女、他、她), but in practice those words are better translated as "that person" then he or she. They are usually only used to emphasize reference to a specific person whose name is unknown.
There are probably many other features which I didn't think of.
I think at least the first few points apply to all the CJKV languages, while the later few may only apply to CJ (the two I actually know). Please correct me if that's the case!
Has the existence (or lack of) of an East Asian sprachbund been discussed among linguists?