Some readers, especially non-Americans, might wonder what the recurring squabbles in Washington over the debt ceiling and government shutdowns mean. That’s understandable. In virtually every country in the world, when the legislature approves a budget that results in net new borrowing of, say, 50 billion euros (US$55.8 billion), the government is thereby authorised to take on that debt to finance the budget. Not so in the United States. There, the budget and borrowing authorisation are two...