You're pretty impatient, johnaus (not even 15 minutes from your original post)! Firstly, they still have their AAA rating and have just had a warning and their outlook changed from 'neutral' to 'negative', so that there's a 1 in 3 chance that their AAA rating will be cut in the next two years (not sure how solid that assessment is). Like anyone buying gold already isn't aware of that risk and doesn't need a US government-sanctioned rating agency to tell them the trouble the US govt is in.
The key question to ask is do you define inflating your debts away as a form of default (through monetary inflation)? The key point about these rating agencies is that the rating given is based on the country's ability to repay the debt and doesn't take into account whether the money used to pay it back is of any true value by the time it's paid back. That is why they have their AAA rating whilst the world's biggest largest owners of their debt have lower ratings than the US (eg China/Japan). Hilarious really. All coming from the same agencies who rated those sub-prime CDOs as AAA just before the GFC tank. Great track record there! This is why short-term price movements in the USD and treasuries like those from the news overnight are irrelevant in the long run.
