America’s AAA-rating on our sovereign debt is useful to the American people. But it also plays a crucial role in the global economy as a whole. People and firms want access to safe sovereign debt for a variety of purposes. If we lose that rating, can people just start using German debt instead?
Basically, no. There’s not nearly enough German or French or British AAA-rated debt out there to play the kind of global role that U.S. Treasuries currently play. The world’s second largest economy, China, doesn’t have liquid capital markets, and the third largest economy, Japan, has already lost its AAA-rating.
[UPDATE] Incidentally, the “other” AAA-rated countries are the Netherlands, Australia, Austria, Norway, Singapore, Switzerland, Sweden, Denmark, Finland, Luxembourg, and Hong Kong. So the issue, as you can see, isn’t so much a shortage of non-U.S. AAA-rated sovereigns, it’s that these are all small countries who are highly rated in part because they don’t have very much debt outstanding.