Russia in 1998 had an economy that was not tied into the global banking system as inextricably as our own, and they got a massive injection of capital from the IMF and Japan. What sort of position do you imagine the IMF to be in if the US dollar collapses? Plus they could survive on barter until the economy got working again. Could this happen in the United States, outside of a James Wesley Comma Rawles novel?
Germany and Japan in 1945 had a rich uncle named "Sam" to lend them a few bucks until they got back on their feet. Who's going to bail us out?
And finally, let's not forget the last time the German economy failed before 1945. The Weimar Republic's currency crashed within a few years, and pandemonium ensued. We all know what the result of that was.
And yes, Germany got back on its feet in the thirties thanks not only to guns-before-butter policy enacted by the newly-elected Nazi party, but also by a huge infusion of capital from JP Morgan. Again, if the US economy fails and the dollar becomes worthless, who is going to bail us out?