Iran is now only accepting euro's in payment for oil, China and Russia are now making trades directly in Yuan and Ruble bypassing the USD.
Russia/China is launching a SWIFT replacement.
Zimbabwe has dumped the USD for Yuan as a currency.
The USA will lose reserve currency status then your USD will be worth less than toilet paper before you know it due to drowing in debt.
Reality check:
1. Half of Iran's assets are still frozen by the US and other countries, about $50 billion dollars. Of course they don't want to trade in dollars, Iran's biggest trading partner is Europe. Russia the largest oil trading partner with China. Do you know who the #1 producer of oil in the world is? The United States.
2. SWIFT is an international transfer system that is not run by the US and which doesn't have much to do with the dollar. It is under the law of Belgium, if I remember correctly.
3. Zimbabwe did not dump the US currency at all. China forgave $10s of million in debt if they would also use the Yuan as a currency. Zimbabwe uses the South African rand and dollar as currencies and will continue to along with the yuan.
4. There is zero chance the US dollar will be worth "toilet paper" any time in the future. The US dollar has appreciated against almost all major currencies in the last 5 years including the Euro (1.5 -> 1.1), Japanese Yen (1.2 -> .87), Canadian dollar (1 -> .72), Swiss Franc (1.3 -> 1.01). Against the Yuan it's basically been flat in the last 5 years because the Yuan went up and down. It peaked around .165 dollar/cny and is now .15.
In the last 5 years, the Russian ruble has collapsed against the dollar. From .034 dollar/rub to .01 dollar/rub