Japan is 1.67% world's population and US is 5% of world's population. Why bother with them?
Thats' exactly what Bitfinex did with US traders around fall of 2017. Pulled right out of the US and asked all US accounts to go elsewhere. That's the safest way to go, I don't blame them or HitBTC one bit. Plenty of business worldwide so why take any risk at all. Easier to eliminate the extra headaches.
RE: HitBTC suspends service in Japan