The dollar is also backed by the legal system (which gives the general populace a mechanism to redefine who owns which dollars, e.g. in case of fraud), and the Federal Reserve (which manipulates interest rates and dollar supply levels to try to keep the value relatively stable over time).

If bitcoin could solve those problems, and the energy usage problem, I’d use it. As is, it’s solved the double-spend problem - admirable and impressive, but it’s not a substitute for a stable currency yet.

Americans have to pay taxes with them, even if we get paid in gold coins or cryptocurrencies. If you don't pay you can go to prison. Therefore, owners of dollars can know there will be at least some minimal demand for dollars in the near future.

Sure, but its also backed by a few aircraft carriers, ICBMs, ~ 1.3 million warfighters, and a few other things ;)

I find that to be a somewhat reductionist view. First, some things have a fundamental energy cost. Food is one example. You can’t value food for free even if we agree to, because it takes kWhs to produce it and they have to come from somewhere. I guess you could say your life isn’t worth the cost of the food to sustain it and stop eating it, but not many will do that.

Second, you have natural scarcity: truffles are not commonly available. How much you want to eat them may put a ceiling on the price, but again there is also a floor below which no amount of energy would bring you more truffles.