Our colonial empire is falling apart. You really need to open your eyes.
The US dollar is used for oil and other commodities because we were once the primary supplier or consumer. After WWII, with Europe's and Japan's economies wrecked, the US granted generous aid in the form of the Marshall Plan and tolerated unfair access to US markets as a way of bolstering allied economies and and anti-Soviet political alliances.
So even before WWII with Japan, we restricted or loosened trade with the US in pursuit of political goals. We were so much more trustworthy than the European colonial powers that the Saudis formed Aramco with the US because they saw the US would not rob them blind, unlike BP, Royal Dutch Shell, and the French oil companies. We didn't even blockade Cuba (except for Soviet missiles) and simply cut off trade.
The outflow of dollars (trade and investment deficits) is what made the US dollar the "reserve" currency. When do you think China or India or Europe will ever run trade deficits to enable such a reserve to be built up? Never. The BRICS will always be a barter system, a COMECON v2, where Russia for example exchanges oil and gas for Chinese made goods, with China eventually squeezing Russia for all it can get, just as the Soviet Union squeezed its Warsaw Pact vassals.
The big difference now is that we tried the unfair trade route to mollify the Chinese leadership. This policy has been a catastrophe for the United States and has created an enemy that rivals the US not only in military but also economic power.
That's really what the BRICS are about: forming an economic bloc capable of operating without political pressure from the West, which in fact will result (if it succeeds at all) in its members become economic vassals of China, a far worse and more dominating thief than the US has ever been. As an association of thieves and leftists, it has little chance of long term survival as long as the West maintains some form of unity.