Cryptocurrencies are fiat currencies, like the modern dollar. Unlike the gold-backed dollar of yesteryear.
Major differences:
Most cryptocurrencies have guaranteed rates of inflation and predetermined supply.
National governments may arbitrarily create massive inflation (hidden, flat taxes) as they feel like it, to fund their agendas.Most national fiat currencies use coercive methods to guarantee their populations trade in their currencies.
Cryptocurrencies rely on being so appealing that people voluntarily adopt and use them.National currencies rise and fall with relative national economic standing of the nation. A global currency could only fall if it were being supplanted in usage on a globally relevant scale by another currency.
I believe that a global cryptocurrency is better for the people of the world, but I'm not convinced that national governments and dollar-rich billionaires will lose the fight for control over the world's money supply. In fact, if I had to place a bet on the ultimate outcome right now, I would bet on national governments, in an unprecedented show of international cooperation, outlawing decentralized currencies.
But, can we all stop talking about the dollar like it's some ancient bulwark of unshakeable value? The modern dollar has only existed since Reagan, and finances have not been going so great for typical Americans or the U.S. government since then. Maybe it's time to melt down that idol and look for a better monetary system. And at the very least, let's not pretend that fiat is in any way more "real" than cryptocurrency.