The dollar just ledges itself, since it's not backed by gold anymore. Most dollars are just entries in a database somewhere (and I would argue that paper dollars are really a distributed kind of ledger too).
Some people claim the dollar has value because the government accepts it for taxes, but the IMF's SDRs function as currency (within an exclusive population), aren't backed by anything, aren't accepted for taxes by anyone, and are worth $300 billion.
Some people claim the dollar has value because the government accepts it for taxes, but the IMF's SDRs function as currency (within an exclusive population), aren't backed by anything, aren't accepted for taxes by anyone, and are worth $300 billion.