Of course it's going to badly impact the US dollar, just how severe should be the question you should be asking. These countries that have become part of the BRICS alliance do not have the best relationships with the US ever since, and yet despite that they still depend upon the US economy a great deal. So in that regard I still think there will be a substantial impact upon the US dollar should they continue with the ditching of USD. One can argue that they could bar the US from receiving export and resources like oil, which will severely affect the US economically, but I don't think it's oil that will be the biggest denominator in this battle of attrition really. Especially when the world's turning towards electric vehicles and everything that's automated.

I think what could really affect the US economy here is the prospect of a formidable foe that could thwart the western superpower economically and in the military sector. Much of the countries in the BRICS have their fair share of nuclear warheads and weapons that they can detonate at their disposal and since the US is basically fighting in a 1 vs. everyone situation here, the mutually assured destruction caveat don't apply.