I disagree that irreproducability is the key. The central part of "full faith and credit" is the fact that the US accepts US dollars as payment. Which is import

I disagree that irreproducability is the key. The central part of "full faith and credit" is the fact that the US accepts US dollars as payment. Which is important, because it can place debt obligations on people. In short, the US guarantees that there will always be a buyer for dollars. Bitcoin does not structurally guarantee that there will always be someone else who wants to buy Bitcoin, you have to take that on faith.