>>But mostly, the war ended when the governments and economies of the nations fighting could no longer withstand the strain and started collapsing. (Russia is the most obvious example; Austria-Hungary and the Ottoman Empire were sketchy going in; Germany and France were the military superpowers but Germany finally fell apart with France about this far > < from large scale mutinies. Oh, and Britain finally paid off its WWI loans in like 2015.)

Huh? Germany lost. It couldn't have defended its territory by the time it surrendered. Britain and France could have easily fielded armies of the same size into 1920 if needed. There was no financial risk for them once America entered the war. The mutinies for germany began once it was clear that the war was hopeless. In comparison, the mutinies the french arm had suffered in the aftermath of the nivelle offensive were long gone by this time.