The government is NOT REASONABLY allowed to renege on this promise as it is a fundamental part of the binding contract between the parties. If the government does so, it means it's current shape and form does not respect contracts.
The government has the right to repudiate its debts. The political fallout of doing so is what keeps this right in check.
If the public trust in the governments to follow thru on the "100k insurance plan" is viewed skeptically, money moves. It always moves to safe havens. It does not have to be a specific critical event that causes the loss of trust, it could be any of a number of things.
For the interests of power mongers, it is far safer for a government to print money than seize bank accounts, in my opinion. Since then the problem is that the nations using the Euro cannot print, then the Euro cannot keep pace with the US printing and nations using Euro can only go for debt.
Does this mean the Euro will necessarily collapse?