If and when cryptocurrency finally becomes an official global currency, how do you think it will affect the global economy and the economy of each countries? Will it help improve the economy better than fiat or will it still need help from fiat?
It depends on what you mean by the official global currency, which will become the crypto currency. It is necessary to proceed from the fact that states will not widely use the decentralized crypto currency in their financial activities. It seems that it is unlikely to be widely used and private business. Decentralized crypto currency is too volatile for this. As a global currency, only citizens can use a decentralized crypto currency.
In this capacity, decentralized crypto currency is unlikely to have a strong impact on the economies of states.