I think you have this backwards: the US was helping considerably, and then got taken over by pro-Russian conspiracy theorists.
But the bond stuff isn't "tribute" or nationalism; remember, it's being made by private sector investors, not national governments. Fairly straightforward calculation: which way is the exchange rate expected to move? Interest rate? Risk of default?
Up till now the US offered moderate interest rates, favourable direction of exchange rate movement, and imperceptible risk of default. There's still no reason to default other than madness and a desire to strap on the suicide vest and become Argentina.