Let's give some things definitions so that we are on the same page. Americans and westerner countries are abit confused I believe about what gives their currency value. The first thing to clear up is as of right now there is no western country that can take Chinas place in the global trade world at the moment. China holds all the cards, they own the supply chains globally of most the worlds commodities except oil and most of the knowledge needed to manufacture at a profit. Any western leader talking about decoupling from China and the growing economies is lying to their citizens to get them fired up and to get their support. It will take a decade or more to catch up to what China can do.

So that leads us to Brics, brics is a legal frame work amongst the leading commodity and technogy providers that make the world go round to trade with each other even if the US dollar is absent. They aren't trying to replace the dollar, they are legally making secure routes and ideas to make sure its business as usual even if the US decides to attack or cut members off through things like sanctions. Russia being able to sell oil through India is an example of this. Europe still needs Russian oil they just have to buy it through a brics nation.

If trump wants to cut off trade with brics countries that's only going to lead to shortages of commodities and manufactured products coming from those countries. Yes they won't have american dollars but America and Europe will also not have any goods to sell for more than decade. China and Russia are smiling ear to ear at the thought of a trade war at the moment.