BRICS will never introduce their own currency anyway, so any threats by Trump are moot. Can you imagine India and China actually agreeing on a new currency structure? Lol, it's a total fantasy.
I can certainly imagine China creating their own and making the others use it. I can also imagine Brazil trying, though I can't imagine it succeeding.
Brazil has gone through numerous currencies. They have all gone to zero due to hyperinflation. One of the top Brazil stories on HN is about the way the government conned the population into believing that this time it was going to be different. We are also about to launch our very own central bank digital currency.