DaveMart - "real change will probably arrive via a 1789 style purge"- you are probably right.

It is the aftermath of such a purge,bloody and brutal as it was with a lot of collateral damage,which is problematic.Napolean rose out of 1789.

Although history can teach us many lessons the present situation is unique with it's multiple severe stressors.

Also,a question - If a meltdown occurs in the US as is becoming increasingly more likely,what are the chances of,and the likely outcome of, the US government of the day declaring a moratorium on national and international debt?

Virtually nil, in my estimation.
They will instead simply inflate it to worthlessness, but never admit that the debts are irrecoverable.
I know little about these matters though - check out memmel and Gail's posts for a thoroughly knowledgeable, although rather depressing, estimation of this sort of issue.
Euan also intends an article on the ruin that used to be the UK economy, I believe.
I recently posted graphs of the UK financials showing budget deficits and balance of payments, which would all be bad if we were about to enter the sunniest of financial times, instead of trying to keep our head above water in a world of greatly elevated oil costs.

Both for the UK and US my estimate would be that the wheels come off by this winter.