The value of a given collection of bits is whatever you and I agree the value of those collection of bits is. It's a one to one relationship.
The value of USD is not what you and I agree the value is, it's what the government tells us what the value should be. This is not a one to one relationship.
One is based on a transparent mathematical equation between you and I and the other is based on 7 non-elected and appointed board of governors between you and I. That's the difference.