For years, Americans have been warned that the national debt is unsustainable. The warnings have become so routine that they are easy to ignore. Congress approves another spending package, the Treasury borrows more money, and the federal government continues operating as though there will always be another buyer for its debt.

For years, Americans have been told the economy is stronger than it feels. The stock market keeps climbing. Headline unemployment remains relatively low. Washington points to GDP, consumer spending, and official inflation data as proof that the system is holding together.