I don't see crypto-currencies making governments obsolete, just smaller. Without the ability to borrow on a massive scale or impose an inflation tax and with the difficulty of enforcing an income tax, they'll have to rely on other sources of revenue like sales taxes and property taxes.
I agree, some governments will be hit harder than others. The ones that will suffer greatly are those that wager half their nation's economy on a
military industrial complex, since they are entirely dependent on never-ending inflation to feed the monster. These types of violence-prone governments will be the hardest hit by the forced obsolescence of their fiat scrip. Places like Sweden will survive the transition relatively unscathed.