No, at the moment, they could not. Value of cryptocurrencies keep changing rapidly. If value of national currency is tied for example to Bitcoin, it would have very negative effects on country's economy. In the future, when value of cryptocurrencies stabilizes, it might be possible, but at the moment it would be a big mistake.

Also, relative to the size of the US economy, cryptocurrencies are not big enough to have a significant effect. This need not be true for smaller economies/currencies.  

I am not sure if we even know the answer. Nobody can affirmatively say the impact the Betcoin could have on any economy without reviewing actual studies on the subject matter. Any statement one proposes here is just a pure guessing and serves no purpose but speculative.

Thanks

I think the literature is fairly clear that the transactions themselves do not matter for the value of a currency, but the demand for inventory of a money does. So dollar credit does not so much affect the velocity of money as people shift from using dollar currency or dollar deposits to dollar credit, to say a credit card. What matters is that someone is holding dollars to pay my credit card charges instead of my holding it, so the total demand for dollars is not affected by whether I hold and use dollars or a creditor holds and uses dollars to pay my credit card charges. The same is true if we imagine buying French goods in France in euros or buying them in stores in the US using dollars. No effect on the demand for dollars or euros. 

If the demand for bitcoin holdings rises relative to dollars that is a different matter. As noted above, however, that is not happening in two very important senses: the quantity of bitcoin is very small relative to the supplies of most currencies and transactions using bitcoin are not affecting the demand for any currency relative to bitcoin. So far, perhaps mainly due to tax policy, bitcoin are not much of a substitute for dollars as money because of the volatility and because of the tax treatment of bitcoin as an asset in many countries. So far bitcoin is not money, even though it is used in some third party transactions, because it is a poor store of value or as Friedman put it, a poor "temporary abode of purchasing power." 

I believe the best answer you get is the answer from John A. Tatom ,

I consider the bitcoin as a product you buy it using other currency most likely the dollar. the bitcoin now reflect a real value and most likely a dollar value.