1. Language: the two languages are not in the same language family. The word orders are radically different even though 60% of Vietnamese vocabularies came from Chinese. The Vietnamese experimented with several different writing systems. First Chinese character, then Chu Nom, and now Latin alphabets.
2. Food: historically Vietnam is geographically isolated and small in area. So they developed their distinct cooking style. There are some overlap in dishes with bordering southern Chinese provinces such as pho, but the raw meet and vegetables often found in Vietnamese dishes are nowhere to be found in China.
3. Music: the traditional native Vietnamese music are very distinct in style and can be easily differentiated from Traditional Chinese music.
4. Literacy: for China, the civilization and literacy is continuous and un-interrupted. So a Chinese can still pick up a book written three thousand years ago and read them without much difficulty. Reading countless fictions and texts passed down from the old days is a big part of the entertainment for ordinary Chinese. This creates a sense of belonging and desire to live on with tradition. Also, in a way, all Chinese are historian themselves, as they can read and study the original historical texts and form their own opinion just as what professional historians do. For Vietnam, the language went through great shift several times in history. Nowadays, what's available for Vietnamese readers are all translation of old Vietnamese text which is like another language. The writing system has changed from logographical to alphabetical. The literacy value cannot be passed on between the two vastly different system. So old Vietnamese literature mostly only retains their value as recording of historical fact for scholars and has lost connections to the general public. The modern day Vietnamese can only learn their history through the government and what historians choose to write in textbook as they has no other ways to confirm it. So it is a lot easier to manipulate public opinion and sentiment on history. Chinese government never tries to do this, as they know it is going to be fruitless.
5. Status of women in society. In China, there are a lot more men than women. The communist rule and one child policy has raised women's status to be on par with men. Even the average education level for women is higher than men in China. In Vietnamese, its the other way around. There are more women than men after decades of war and so some men can have several wives. Women's status in family and society is a lot lower in Vietnam.
