I always bring up Somalia. The government crumbled and they continued to use local paper currency even after the printing presses were destroyed and there was nothing backing it. In the actual global collapse scenario, physical cash is likely to be more fungible and still have value than gold.

So if you really want to prepare for that (which should be like step 156 in terms of prepping), the right solution after you have all your direct physical needs (canned food, medicine, etc.) is simply a cash stockpile.