Why the US economy is ringing alarm bells

What with a 250th birthday, Taylor Swift's wedding and the football World Cup, Americans could be forgiven for taking their eye off the ball this summer. But signs of economic trouble have been building. This week they hit the headlines when US national debt passed the $40tn (£29.4tn) How did we get here? It took almost 200 years for US national debt to reach $1tn for the first time, says Maya MacGuineas, president of the Committee for a Responsible Federal Budget.