Russia’s war in Ukraine, Vladimir Putin and Xi Jinping’s recent meeting in Moscow, and China’s apparent success in brokering a diplomatic rapprochement between Iran and Saudi Arabia have fuelled renewed chatter about threats to the global primacy of the United States – and particularly to that of the US dollar.

I encountered such commentary in the responses to my recent Global Policy article assessing the future of the BRICS (Brazil, Russia, India, China, and South Africa). The group is now considering an enlargement that would bring in countries like Iran and Saudi Arabia, raising questions about its criteria for member...