From what I understand, the US Dollar is backed by: The IRS requires taxes be paid in dollars. It's a federal offense to refuse payment in dollars for purchases under US jurisdiction. The US has negotiated other countries to require payment in dollars for oil and maybe other goods. The world generally has confidence in the dollar as a fairly stable currency that is unlikely to collapse.
What did I miss?
My understanding of what backs Bitcoin is: By mining Bitcoin, you are provably putting yourself into a financial loss and therefore are provably motivated to turn that around into a profit. Buying Bitcoin is also equivalent to mining in this regard. That means around the world, millions of people are motivated to the tune of nearly a trillion dollars to ensure that the system continues to not only keep working, but grow more valuable.
What did I miss?
My understanding of what backs Bitcoin is: By mining Bitcoin, you are provably putting yourself into a financial loss and therefore are provably motivated to turn that around into a profit. Buying Bitcoin is also equivalent to mining in this regard. That means around the world, millions of people are motivated to the tune of nearly a trillion dollars to ensure that the system continues to not only keep working, but grow more valuable.