James Joyner writes, Arnaud de Borchgrave and Thomas Friedman notwithstanding, the U.S. is probably not in permanent decline. It includes this impressive graph, and while I can't personally vouch for the numbers, I've seen similar graphs, at least for the post-1900 period:
Second, part of the current problem seems to be that banks are hoarding cash. And part of the reason for that may be that they are waiting for settlement of the derivative securities created by Lehman and other failed firms. Supposedly, Lehman securities will be settled this Friday, and the Feds are working on creating a central clearinghouse.
Those things may help, but don't, on my account, bet on it.