Warning: This is a long lecture but it's well worth it. History usually repeats itself and if it doesn't then it almost always rhymes.
Niall Ferguson is a Harvard University history professor who has done a lot of work around the rise and fall of empires from an economic perspective.
As you will see below: The similarities of what we have seen in the past from a debt perspective when we compare our current economic collapse with previous famous historical collapses is frighteningly similar.
Debt payments continue to rise and eventually overwhelm the countries GDP. Niall calls this "Game Over" time during his speech. At our current rate of spending, Niall explains that 85% of our total revenue would be needed in order to simply service our debt by 2050.
He also explains that we are in a worse fiscal situation than Greece. There is also a great Q&A at the end.