A crash is possible if USA Russia and China all agree to out law it.
Russia is totally irrelevant. China have already sidelined themselves. The US outlawing it would be one of the weirdest moves of modern times.
First off, there is about zero chance that Russia would outlaw bitcoin since they just approved a law legalizing it.
Granted, they made the law so they cannot use btc for goods and services DIRECTLY, but it is the same as to say that $ is outlawed in Russia because $ cannot be used to buy goods and services there as well. Of course, $ can be exchanged to local currency (rubles) anywhere (banks, kiosks, etc.), I went there for the World cup 2018.
smame, I assume would be for btc. Mine, buy, sell on exchanges, then exchange to rubles to buy stuff.