The last one -- Bretton Woods -- happened at the tail end of WW2. I'd imagine WW3 or something equally destructive would be required to totally upend the system.
The dollar is the worlds reserve currency. It would start with the dollar being severely devalued. What happens after that is unpredictable. One thing holds true however, gold will still be valuable after that.
People have been using money since before recorded history, and bronze age technology is sufficient for gold to be used as reliable money. If any kind of financial system is to arise from the ashes of civilizational collapse, it will almost certainly use gold. So I wouldn't say "meaningless"... just not immediately useful, perhaps.
Assuming you’re talking civilian tossed back to the Bronze Age. Whoever has access to the vault might make use of the gold in such situations, but ownership is unlikely to be tracked back to people in another city etc.
Now, if you personally want to store physical gold that’s a different bet. Though personally storing significant amounts of valuables like that has plenty of obvious downsides.