China is a country that takes up most of the area in South-East Asia. Civilization in China dates back as far as 2700 B.C.
As far as its influence in Japanese anime goes, China has been used in quite a few shows. For example, Shanghai was the main setting for the anime of CANAAN. In G Gundam a young teenage pilot represented the country of China in a bid to restore the teachings of the Shaolin temple.
The Three Kingdoms period, where the nations of Wei, Shu and Wu fought each other to control the whole land, is romanticized and twisted for use in several anime, such as the Ikkitousen franchise.