I guess 1 or 2 years ago, America was the country that has the most transaction in Bitcoin, cause Bitcoin at the moment was used by hackers on the deep web. But now things are changing cause Bitcoin are more popular for now and maybe Japan has the most Bitcoin transaction ? Because their goverment accepted Bitcoin as an official method payment maybe ?
The regulation done by Japanese government really helped their trade market. It shows how users are ready to switch pretty fast to any available means to make use of the digital currency and it is good. China though will still have a comeback and that is for sure with some regulatory policies and that should really cause some little boom or maybe the Chinese traders moving in back with Yuan.
It really helped them a lot and it also coincided with China's shutting down of exchanges which to me was well played out by them. It has really pushed their currency to the top volume traded with BTC and I am pretty sure since it is regulated, that means a lot of improvement even for their economy at the long run. Wish some other countries will start using them as a case study for implementation purposes.