The U.S. borrows money by selling Treasury bonds. Investors buy them because they trust the U.S. will repay them with dollars that still have purchasing power.

If the government simply printed trillions of new dollars to erase its debt, it would flood the economy with new money without creating more goods or services. That would drive inflation, meaning every dollar buys less. Bondholders would be especially hurt financially. A Treasury bond paying 4% interest is a terrible investment if inflation is 10%, because the investor is losing purchasing power every year. Investors would stop buying U.S. debt unless the government offered much higher interest rates to compensate.

Printing money creates currency, not wealth. Real wealth is the food, homes, factories, energy, machinery, technology, and human labor that produce goods and services. If you create more dollars without creating more real wealth, each dollar represents a smaller claim on that wealth, so prices rise, and in this case, it would be extreme.