Nanzhao was a country. It has since been destroyed.
It is sometimes referred to as Nanzhou.
Internationally, Nanzhao's reputation was one of a brutal regime which endorsed an international drug trade.
Nanzaho's government was overthrown by Cobra,before the group began dropping nuclear bombs on the country to not only end the local drug trade but cement Cobra's place as a nuclear power.
Cobra Commander eventually unleashed nuclear weapons across the entire country, devastating it completely. Unknown to all, the act was done to erase all traces of his past life and thus, any sentimentality that might have been left inside him.
The nuclear devastation of the country was considered only second to the destructive fallout of Megatron's invasion of Earth. After Cobra Commander revealed G.I. Joe's existence to the world at large, the group was hated and distrusted by the public as a result of Nanzaho's destruction.
The event remained a sore spot for the Joes even years later. When various world leaders had assembled at Autobot City to meet with the Junkions, Mainframe commented that more weaponry was present than there had been at Nanzaho.
- Nanzhao at the TFWiki