> If blockchain based currencies prove themselves to be a significant improvement on current monetary systems then state currencies, such as the US dollar, will adopt the new technology, as they have done with all other previous developments in money.

The US dollar, as such, often hasn't adopted new developments in money transmission directly (at least, not at the consumer level); the circle of businesses facilitating USD transactions has, but a dollar-pegged cryptocurrency is essentially just a new part of that ecosystem.

OTOH, the dollar has adopted, directly, new tools in money supply management, several times in its history.