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Talking about Russia, even if they are a big source of oil and are good competitor of the USA, but still they might have to trade using US dollars while making trades with the US. Overall, I don't think US will be in any danger if these countries will starts to make deals in local currencies, that's because they ways to make deals in local currencies are full of difficulties and these difficulties will increase more by the ones who might be in danger due to this.
You bring quite an interesting perspective. It is true that even though Russia is the US's main competitor in energy resources, they still trade using US dollars in international trade, however I think cooperation is not always in line with political relations.