Almost all bitcoin trading is done in China. but officially banned now by chinese govt.
Even before trading volumes isn't just can only be found on China, we don't even have statistics on it. But that's one factor of it that the possibility that China has the most trade volume in the bitcoin economy or for the whole crypto market.
But later on after the adoption of Japan and South Korea I'm looking at these two good countries that they are now dominating the volume of trades in the South East Asia but with the other continents, I don't have an idea on what country has the most trade.