Sinosphere is a very real term. It doesn’t mean that China is the strongest and the best. It just means that this is a sphere of influence that was started by Chinese culture.
Every aspect of Chinese culture was adopted by surrounding countries, just like how modern people adopt American ways of life, down to the language, clothes, food, and entertainment. Chinese arts, language, food, and fashion were spread throughout East Asia. However, the ones most influenced by this cultural power were Korea, Japan, and Vietnam. Ryukyu was also part of the Sinosphere, but was later absorbed by Japan.
To put things in simple terms, all of these 3 nations started their borrowings during Tang. However, by the start of westernization:
- Japan is most influenced by Tang and Song cultures. (Japan stopped borrowing from China once Yuan dynasty appeared)
- Korea is most influenced by Yuan and Ming cultures. (Korea stopped borrowing from China once Qing dynasty appeared)
- Vietnam is most influenced by Ming and Qing cultures. (Vietnam continued to borrow from China until French colonization)