In my opinion, such a comparison makes no sense. Why did you decide to equate the amount of money supply in dollars to the total supply in bitcoins? Why such a comparison can not be made to the euro, yuan, or other currency? And what is the practical meaning of this comparison? There is no relationship between the volume of money supply of any state and the volume of cryptocurrency.
The OP is not comparing. The OP is using USD as an example for their idea. They are rather comparing the volume with the % of the currency owned. Not the volume of fiat to the volume of crypto.
It is a fair idea the OP has. They are talking about the currencies divisibility.
The idea of OP brings argument in the table. People saw the flaw of the calculation and state their disagreement. I too think that it is not accurate to come to that value since the actual value of a certain asset is not derive from the comparison of supply. One may be rarer but cheaper than the abundant one because of their use case.