I'm not trying to scare anyone, I think people just need to be aware that it's a distinct possibility that we will either have another depression like era, or also possibly be forced into a new international currency, but that's not on topic.
The national debt does play a role, because the government is part of the economy. The bailouts they take part in are essentially them fucking with the market. Leaders (in general) in this country refuse to deal with the economic consequences of some of the bad choices made by either companies themselves or by policy voted in. We prop up bad decisions instead of allowing the natural course of the market to take effect.
You're right about the housing bubble, but that's just one of many bubbles we've been keeping afloat. What happens when they all start popping, as they inevitably will?