Having a legal right to the collateral isn't the same as getting your hands on it. Payments won't be "cancelled," but "delayed due to unforeseen circumstances."How fortunate for US bankers that there was a push to only make secure loans. Just means they end up taking the collateral for the French loans so not a total loss. I imagine some of the French gold reserve was also put up as collateral which could lead to interesting things.
Any loans that were written in francs or pounds can also be wiped out by deliberate inflation.