I think we are headed towards blockchain and crypto based coins inevitably. As globalism continues to rise, we have no other choice but to adapt a single currency monitored and regulated by everyone and none would have supreme authority over it.
The US dollar is a messed up thing. With too much risks, I would never store fiat cash under my bed because it's just too risky and will lose value. In India we had demonetization where 500 and 1000 rs notes were banned which showed me how fiat is useless concept!
I am not an economic expert but I think us dollar loses its value due to the debt of USA. The federal reserve of US continuously decreasing and in fact, China has a lot federal reserve. When USD messed up, inflation may occur in different states in US. To prevent this, printing of money would not solve the problem. But it adds more a lot to become hyperinflation that cause their goods and products more high. Digital currency will solve the problems in fiat. By the time that we will all adapt the single currency.