I disagree. A lot of the US dollars that are held outside the US seem to be held not with an intention of spending them in the US, but out of trust that everyone will always agree they're valuable.
USD has inherent value* because it can be exchanged for goods, property, and services in the US. Or to pay US taxes. The US has a lot of goods, property, and services that people want. US taxes are not a consideration for most people outside the US.
*Since most global trade is denominated in USD, and many countries use USD as their official currency, it can also be used to pay for goods, property, and services outside the US. But arguably it wouldn't have this global status if the US itself didn't have valuable goods, property, and services.
That's pretty much the only reason anyone has for taking any foreign currency.