> up until Russia's currency was so successful that it did indeed threaten the US hegemony

That's not remotely plausible. Russia doesn't have an economy to support a serious global currency. It has an economy the size of Canada. The US could have never positioned itself to have the global reserve currency, without having the world's largest economy (or otherwise massive economy). That position dates back to ~1890. You can't acquire a superpower economy on the back of currency magic, it can only be done through actual economic production (an area where Russia is severely lacking).