At the moment the US dollar is effectively used as the international reserve currency. The dollar has become the main currency of the global economy. And that is fraught with danger. As the central trade currency the dollar helps reinforce a model of neocolonialism that's already in place. Take debt for example.
Nations create wealth internally but they have to service their external debts in another currency.
That means relying on exports to bring in the foreign exchange necessary to service this debt. Which is why debt is such a burden in the global economy. An ICB would allow each country to pay for cross-border transactions in its own currency and so bar speculators from raiding the world's currency reserves. People could then create wealth in their own currencies within their national economy and be able to have equality of interaction with the rest of the world. Export-led growth has come to dominate the global economy.