To me, it seems there are two sides to your point, one about trust, and the other about dollar value in context to growing federal debt. As for the trust, I think part of where things go beyond trust comes from a sort of self-reinforcing economic strength.

When the average monthly expenses for an American household add up to about $5,500, certain industries (like transportation (16.8 percent of those expenses), or food (12.8 percent) will always view the American economy as a leading market to operate in. At a macro level, it would seem that many businesses making this similar judgement call would create a dynamic that goes beyond trust.

Regarding the buying power of pensions point, I believe there are cost of living adjustment laws for buying power which require Army or Social Security pensions to react to USD's changing buying power over time.