I've heard that us dollar will collapse in near future. History has shown that national currencies do become worthless, for example the deutsch mark.
The dollar is no longer backed by gold, and since the brenton woods agreement, oil is priced in us dollars, so if a country wants to buy oil, they must first purchase us dollars, thereby creating a demand for dollars. The federal reserve keeps printing money out of thin air, devaluing the currency further and further. Some nations are moving to trade oil with their own national currencies, which usa considers a threat.
I'd like to read what
@blueberryrose has to say about all currencies collapsing.