I'm wondering if federal institutions are going to degrade to the point where I don't need to pay taxes anymore and they will not be able to enforce my not paying my mortgage
They will send the military mafia for their "protection money"
Who needs taxation when they can charge a 50% flat tax just walking around, and using "enhanced interrogation techniques" on people who tries to hide their money.
If the American government falls, completely, if every American official is killed, if the borders dissolve into slurry at the approach of millions of Gothic tribesmen, if civilization collapses, if you are reduced to subsistence farming with a stick and a hand sickle...
... the tax and debt collectors will still be on your ass.