What is interesting in the news of the downgrade, is China's reaction.
China, the world's largest holder of US debt, had "every right now to demand the United States address its structural debt problems and ensure the safety of China's dollar assets," said a commentary in the official Xinhua news agency.
"International supervision over the issue of US dollars should be introduced and a new, stable and secured global reserve currency may also be an option to avert a catastrophe caused by any single country," the commentary said.
http://www.bbc.co.uk/news/world-us-canada-14428930
As the song goes.. "There may be trouble ahead..."
(S&P normally limit the rating of any company to that of the country it is resident in - I haven't checked, but this decision if applied to the USA could mean downgrades to all the AAA companies in the USA. If they don't, S&P aren't playing fair - but that is another issue).
Cheers,
Shafique