A full dinosaur like event is extremely unlikely. Gold is just good if your fiat goes belly ups like with Germany. Even if your country -does- collapse, the neighbouring ones would impose order. And your gold won't loose value. Your fiat may.
If those are fallen too, like a hypothetical meteorite hitting Straya, than those farther away would take charge eventually.
Also, remember. Currencies can be replaced. Perhaps the USD would be replaced by the United States Shekels, USS. It is very unlikely, but still -more- likely than the US collapsing into mad max land.
But if you want to look at what can happen, just look at the loosers of WW2. And those nations had it harder than a bank collapse.