Brad Setser says this about these three countries:
"the private markets don’t want to finance a $900b US deficit at current US rates. Not when the BRIs offer a better return. But right now the private money flowing into the BRIs gets sent back by their respective central banks to the US and Europe. The BRIs, by paying more for money borrowed from abroad than they get on lending those funds to the US, effectively subsidize both speculators bringing money into their countries and the United States. To me, it is nuts."
Also: " One thing is clear: the willingness of the central banks of Brazil, Russia and India to turn private flows seeking yield in their markets into demand for US treasuries and agencies has become an increasingly important component of the global financial system. "
I agree with both statements. I think the key is that the central bankers of these countries see the US as the safest place to park the cash; even though all three countries have major political issues with the US.