As John Michael Greer points out in a recent interview, the significant thing about Diamond's example cultures - the Greenland Norse, the Easter Islanders, and so on - is that they were all very small (less than 50,000 people) and very isolated cultures. So their collapses when they came were fairly rapid, over a few years - and correspondingly violent and unpleasant.

Would larger cultures be different? Surely - they have more resilience, more connections with other cultures to help them out. The historical examples of larger cultures of tens or hundreds of millions of people - the various Chinese empires, the Roman Empire, the Mayans and so on - took a century or more. Rather than everything falling apart over a year or two, it was 20-30 years of troubles and collapse, followed by another 20-30 years of stability and partial recovery, and so on.

What that means is that even if the US chooses to fail, it won't be overnight - and after today's failures, tomorrow may bring partial recovery.