China is a much bigger threat to our dollar hegemony. Russia has the world’s 8th largest economy behind Brazil and just ahead of Italy. It has the 77th highest per capita GDP just behind Antigua and Barbuda and ahead of Croatia.
Russia is however the largest oil producing nation on earth and since dollar hegemony is inextricably linked to petroleum trading thanks to the petrodollar arrangement, Russia is in a unique position to threaten dollar hegemony simply by trading oil and other fossil fuels for currencies other than dollars which they are doing and which, IMHO, is what actually underlies Obama’s ramped up anti-Putin/pro-Ukranian rhetoric. Many political figures have attempted to trade their oil for currencies other than dollars over the past decade or and they’re all conveniently dead now. Putin is a tougher nut however.