Borrowing money is not a crisis by itself.
Households do it for homes and cars, and governments do it to fund wars, recessions, and long stretches of ordinary spending
The trouble starts when the interest on that borrowing grows faster than everything else. For most of modern history, the United States could carry a large debt without much strain. Interest rates sat near record lows for more than a decade, so the government refinanced old bonds cheaply and rolled the balance forward.
Economists called it a manageable burden, and for years it was. Two things changed that math. Rates climbed off their lows, and the pile of debt kept getting bigger.