You really need to stop getting all your information from Russian twitter bots...
I would not say the US is anywhere close to bankrupt (though such things are hard to tell) but I would say the Russians aren't anywhere close to that either.
US still has the petro dollar, and a fairly large real economy to back that up. US as much as people talk about the financialization of the US economy, we still have about $5 trillion dollars of "real" industry (agriculture and industry) and probably another $5-10 Trillion that's much more support for those real industries than "pure" service industries. So, as a rough ballpark even given the most cataclysmic collapse of the financial sector, at least 60% of the economy is "real" and would still be there post collapse and could continue, even if they had to pay their workers in popsicles (product of one of our local factories).
And, since were so rich, a 40% decline in GDP "only" pushes per capita from 70k to 40k per capita. Which is much less painful than Russia's decline from 10k to 6k post USSR.
So, the US going full "we are defaulting on all our debts, sucks to be you" would still have a huge amount left over, and the capacity for extensive domestic production: we're currently run by idiots, but Trump showed we can be energy independent, and pretty quickly and trivially, when the government isn't outright getting in the way. And we have enough federalism left that in such an economic collapse, the local governments still have enough independence (probably) to go "fuck you" if the Fed demanded an economic policy that required doing something or millions freezing to death.
Russia in the similar situation that they do still have significant domestic industry and agriculture, so they can go pretty far on their own way. They also aren't literally broke in the sense they still have extensive reserves.
According to the Russian Bank, they have about $630 billion in reserves, including about $130 billion worth of gold. Total current Russian imports (according to
wiki, ymmv) is around $360 billion, so if total exports were cut off and had to totally pay for imports with current reserves, they theoretically have enough to keep it going for about 2 years.