Warren Mosler explains a bit on how "lending" to the US works: http://www.youtube.com/watch?v=Z1uWVj0YJ3M

Warren and Stephanie Kelton on "governments are not households": http://www.youtube.com/watch?v=ba8XdDqZ-Jg

current "net financial assets" (national debt) are not sufficient for our current level of productivity as evidenced by our unemployment rate.