This is insane and it is not possible at this point in time. It will completely mess up the economy, affecting directly the foreign exchange market. With this also, the role of Central Bank in controlling the supply and demand of money will be compromised which will lead to the government needing to implement rules and regulations on Bitcoin. It is possible for the world to use cryptocurrency as the primary means of exchange but it is not possible to use the same currency. There will be none that defines the value of the currency of US in comparison to the other countries, in terms of economic status.