The United States borrows 40 cents of every dollar it spends. According to the CBO the federal government will spend $1.8 trillion on the wars in Iraq and Afghanistan between 2012 and 2021. In 2011 alone it will spend $366 billion more on defense than China, UK, France, Germany and Russia combined spent in 2009. It will spend $225 billion in interest payments on debt for 2011. Facts like these explain the chart:
For a brief period during the Clinton Administration, aided by the dot-com bubble and higher taxes, the United States has spent more that it takes in since the Vietnam War began in earnest around 1965. Revenues as a percentage of GDP have hit lows not seen in the last half century. We are not only living on borrowed money, but borrowed time too.