The comparison of the Roman Empire and the Chinese civilization is very flawed. First of all, Rome did not unite neighboring groups in Italy as a culture, never mind Europe. The lands and tribes they conquered simply used Latin for trade and as a lingua franca. It never became the mother tongue for any of those people. In China, for thousands of years, you have people from every province celebrating many of the same festivals, educated people reading the same script and Mandarin speaking officials reporting to the Emperor. Furthermore, pretty much everyone in Northern and Western China spoke some variation of Mandarin. The other main language group was Yue in the South and Wu to the East. To add to this, the major historical events in China are much more important than any local ones. Yet, if you ask a French or Italian person about their history, they would tell you very different things.
> The lands and tribes they conquered simply used Latin for trade and as a lingua franca. It never became the mother tongue for any of those people.
And yet, there are 800 million native speakers of Romance languages ("the modern languages that evolved from Vulgar Latin between the third and eighth centuries") in the world [0].
Nonsense. If what you're saying about language was true then the people of France and most of Spain would be speaking a Celtic language, Gaulish or Celto-Iberian.
Instead they speak direct descendants of the language of the common tongue of Roman citizens, 'vulgar' Latin. The pre-Roman languages of most of Roman occupied Europe were extinguished. Apart from Greek, which was kind of the second language of Rome (and later the only language, once the west collapsed) and Palestine/Syria, it's only in Britain where pre-Roman languages survived -- that is until the Anglo-Saxons wiped most of it out, excepting Wales and Cornwall.
Italian, French, Spanish, Portuguese, and Romanian are all directly derived from Vulgar Latin. Japanese is a linguistic isolate, perhaps distantly related to Korean (which is also a linguistic isolate). Japanese borrowed the Chinese writing system, and a little bit of vocabulary; calling Japanese a variation of Chinese is akin to saying English and German are a variation of Latin.
It's even further remote than saying English and German are a variation of Latin, as at least the Germanic languages are in the same family of Indo-European languages. Japanese and Chinese are not related in any way we know of.
It'd be more like saying Finnish or Hungarian are a variation of Latin or German. Some small amount of shared vocabulary (and maybe phonetics) due to proximity, but no more.
Irrespective of the relation between Japanese and Chinese, the immense contribution of Latin found within modern European languages is a given as anyone armed with a dictionary can deduce for themselves.
