Some people already started using the word nuclear for this option of suddenly dumping USD. Like the real nuclear threat, mere deterrence of this virtual nuclear threat can have a lot of impact. It need not happen some time in the distant future, it can happen today, if China wills. This explains why US wants to use us to contain China. As the world learns about this vulnerability of US, it will start losing confidence. We all know that the US enjoyed this TINA (There Is No Alternative) factor as an investment destination and as the world's reserve currency. That may fade. Be ready to see a new world order, bro.
