The issue of U.S. national debt primarily stems from the federal government's long-term fiscal deficit, leading to a continuous rise in the scale of national debt. As of 2025, the total national debt has exceeded $35 trillion, accounting for over 120% of GDP. High debt levels increase interest burdens, with interest expenditure in the fiscal year 2024 expected to be nearly $1 trillion, crowding out other public spending. The Federal Reserve's interest rate hikes raise borrowing costs, further exacerbating pressure. The periodic disputes over the debt ceiling create market uncertainty and increase default risks. In the long term, population aging and rising Social Security expenditures pose challenges to fiscal sustainability. Without reforms such as tax increases or spending cuts, high debt may threaten economic stability and even trigger turmoil in global financial markets.