Earlier quoted context omitted.
And if you really want to boil it down to a single reason, the best candidate would be "becoming militarily dependent on hired mercenaries and then not paying them" rather than something more interesting
I can see that happening. Thinking about Canada. The other day I calculated it would take 25 hours of work for the minimum wage worker to afford a weekend camping. And I think that's a pretty good indication we're pretty close collapse. Workers not being paid enough, and out of control inflation is how the soviet system collapsed.
$1.50 on food per meal.
$1 on camping gas or coal for the weekend.
$200 of gear, but it will last me 20+ camping weekends.
$0 on travel, because I'll be hiking.