Dollar itself has adjusted from a proper link to some kind of unknown backing and is entering its final stage of no backing at all except the willpower of foreign creditors to keep buying debt despite a long term trade imbalance and a potential trade sanction war to discourage trade.      Its all adding up to make dollar prospects unlikely to best over any solid alternative.

The point is these things happen gradually, for example with the USA dropping gold at Nixon's command it still left some standards left for a few years after like the Swiss held a gold backed currency for decades until the end of the century.   They recently voted to return to a gold standard but instead dropped a policy of duplicating EURO money printing which helped restore some value to their national currency.

Other countries will not collapse from just one country.   I dont even think USA will cease for the idea of paper, alternatives will be found and BTC is just one of many hence why its most important it be made as easy to use as possible for a diverse population.   Other possibles are commodity backed currency such as Canada or Australia which in the main are large land masses with centuries of assets to back the worth of a national note.  USA can justify returning from a dollar failure, it just be a hiccup not the grand melt down some might fear.   We will be better of without false dollar value, collapse is not the result but unsuppressed growth.   This is presuming we dont do silly stuff like go to war, debt failing can produce some angry people