1. strong entity circulates and
2. wants back
is fundamentally valuable.
> American dollars have value because the US Government taxes things, like land, and if you do not pay those taxes they will send you mean letters (trust me) before resorting to other means (trust Al Capone). You pay these taxes in US dollars. You just having dollars does not make them valuable. And dollars are not valuable because they are backed by gold or silver or sea shells. What makes dollars valuable is that the government wants them back.
https://hackernoon.com/the-guns-of-bitcoin-1f779309a718
Ways to destroy the US dollar value: Destroy the US tax collecting power, or have the US ask for taxes in a different currency. If the US started collecting taxes in Euros, the value of the US dollar would disappear instantly.
The US is a strong entity and has no incentive to ruin the value of the dollar. It will not start collecting taxes in Euros. Or Bitcoin. Why would it give all that power away? More likely is that Bitcoin gets made illegal or very difficult to use. At the end of the day, if you have US-protected assets, you will have to pay US dollars to the US gov and this will continue to give USD value.
Bitcoin has no such strong-entity backing, so it has no fundamental value. Bitcoin people are obsessed with the idea that mere possession is important. It's not. Ask people with loads of marks or Zimbabwe dollars.