I wouldn't say Bitcoin is even a good example of being able to diversify from nation-specific risks. China's crackdown on the currency is a great example and if the SEC or other regulatory body decides to crack down or otherwise make interacting with these markets more difficult it would presumably have an effect on the price.

The largest risk to the long term viability for bitcoin (and probably crypto in general) are regulatory in my mind. A lot of value can be derived from regulatory arbitrage - just look at the evolution of cryptocurrency's use cases from 1) buying and selling illegal goods, 2) getting around capital controls, and now 3) issuing securities without having to go through the normal IPO process. It's a long road to people using this stuff to transact "real" goods and services. There is a very real nation-specific risk in the form of regulatory regime.