"Like America, when Russia has trouble paying its bills, it borrows money (MMT fans will tell you that Russia doesn’t have to borrow money, but it does). "

Russia will have to borrow in denominations it can't create at will when they are needed. It has no use for its own currency back when spending domestically or in its own currency. A country with a sovereign fiat currency never needs to borrow the currency it can create and the term is a misnomer in such cases.

If Putin can force EU nations to secure rubles to purchase Russia's oil and gas it assures that they will have a continued stake in trading or buying rubles on the exchange market. Either will prevent the forecasted calamity of default. The strength of a currency is dependent upon the non-government and foreign sectors needing that currency, usually to pay taxes but energy dependence works as well.

Other than a basic misunderstanding of MMT your piece is spot on concerning the future of American dollar hedgemony. I, and most MMT advocates, see that as beneficial to the American economy as it will be forced to concentrate more on its domestic well being and abandon globalism, which is just an expansion of neoliberalism and the source of many current economic and political problems.