Almost all bitcoin trading is done in China.

The share of the cryptocurrency that's traded via China's mainland currency escalated over the past few years, overtaking the US dollar as the dominant currency. From less than a 10% share in January 2012, the yuan now makes up nearly 100% of all bitcoin trading.

After china i think almost each country trades with bitcoin. I also heard about some issues with china and vitcoin but im not sure because they were rumors.