This is where I think some back-channel communication needs to be had (on the quiet), that outlines the economic destruction that former allies are willing to take if this unthinkable happens. Crashing the bond market is just one thing. There are many other economic levers that can be used against the US.
Sure it will cause a huge amount of harm to those allies. But it needs to be made clear that this is something they are honestly willing to tolerate, and they’re not joking around.