Bill Mitchell, “S&P Decision is Irrelevant,” Billy Blog, August 8, 2011.This sort of thing happened to Japan repeatedly, but has not affected its ability to borrow at low rates. Nor has Japan defaulted on its debt.
Curiously, I just saw this video below where Greenspan understands the basics of MMT and why there is no risk of US default (from 0.51), where he says:
“The United States can pay any debt it has because we can always print money to do that. So there is zero probability of default.”