At the end, it'll be a currency problem or war. Since US$ shifted from gold-backed to oil-backed in the 70s, it only need to focus on making sure oil is traded

At the end, it'll be a currency problem or war. Since US$ shifted from gold-backed to oil-backed in the 70s, it only need to focus on making sure oil is traded in US$, so other countries has to earn US$ to pay for oil. It would be eye-dropping to see US gov. doesn't print money to pay its debt. If that happens, who knows what's next.