"The cause of [our ruin] is that riches ride on the wind, and have always so ridden in the form of contract deeds, of bills of exchange, of silver and gold, instead of goods that bear fruit and which, because of their greater worth, attract to themselves riches from foreign parts. And so our inhabitants are ruined. We therefore see that the reason for the lack of gold and silver money [here] is that there is too much of it, and [the nation] is poor because she is rich."
The American dollar is not the world's first global currency. It was the Spain peso de ocho, the silver "piece of eight." The above was written in the 1600's about what had became Spain's worsening economic situation. The hundreds of millions of silver pieces of eight that had been minted and put into circulation by Spain using silver mined, refined, and minted in the New World, mostly in Peru.
Niles MacGregor, director of the British Museum, notes in episode 80, "Pieces of Eight," of BBC Radio 4's A History of the World in 100 Objects:
But the very abundance of [Spanish-mined] silver brought with it a new set of problems. It increased the money supply - much like governments "printing" money, in modern terms. Inflation was the consequence. In Spain, there was bemusement, as the wealth of empire, in both political and economic terms, often seemed more apparent than real. Ironically, silver coin became a rarity within Spain itself, as it haemorrhaged out to pay for foreign goods, while local economic activity declined. As gold and silver vanished from Spain, its intellectuals grappled with the gulf between the illusion and the reality of wealth, and the moral consequences of the country's unexpected economic troubles.
Spanish American conquests made possible "the wealth which walketh about all the countries of Europe," that is, silver coin. It is effectively the first dollar, as Barrie Cook, a curator at the British Museum, explains:
‘Pieces of Eight’ is one of many names for the large silver coins of the king of Spain, a multiple of the basic Spanish denomination, the silver real: so a piece of 8-reales, peso de ocho reales, or peso. It is also the original silver dollar, a name that starts out as a place in the Czech Republic in the sixteenth century and ends as the currency of the modern USA.... Pieces of eight pretty much ruled the monetary world from the 1570s till the French Revolution.
Currencies' values fluctuate; currencies come and some eventually disappear altogether. Those are lessons of history worth considering.