The weak link in finance is fiat money. Bonds are a collateral item. If it was needed, the Fed could, and does, put their gold up for loan. Corporations could liquidated their assets. But if there is a panic in the FX markets, there is nothing stopping a run.
When panic hits a currencie, such as the dollar or Euro, the Tresurie bonds strengthen. Look how the dollar is at its lows, while T Bills stay expensive. European countries are having trouble selling their bonds, and the Euro goes through the roof.
If a country wants to preserve its bond holdings, which they do because they hope to use them as collateral once the system crashes (because they will say the other Reserves owe them), then they can continue to spend fiat like the paper is on fire. It is the fiat that will be dumped, and dumped for physical assets. This has been on going, but it will speed up significantly once the newest Fed/Gov policy is released.