I could care less about Goldman Sachs. I do care about the impact of counterparties walking away from their obligations and the resulting negative impact on the broader banking system and credit creation process which would adversly impact the tax base (i.e. small businesses and their employees).
The impact of these "bets" on pension plan returns is tiny. The investment performance of pension plans is driven largely by equity market returns. This is due to the asset allocation decisions and is simply a fact. These "bets" make up small percentages of the overall asset allocation and have had a negligible impact on overall returns (another ice cube you've managed to discover).
You have to look at the whole pie! What is the composition of state and local budgets? Interest expense is tiny relative to other expenses, the largest being salaries and benefits. In a few years, all other expenses will be dwarfed by pension and health payments to retirees. That's the real iceberg - you're merely focused on the ice cubes!