Debt Fueled Economic Growth

EconomPic:

Ignoring the massive spike in government related debt (Federal, State, AND Local) for the time being and focusing instead on household liabilities as a percent of the national income, we see mortgage debt is now at 70% of GDP (more than double the level seen in the 1980's and 50% more than that seen at the beginning of this decade) and consumer debt is now at 18% of GDP.

The importance of all this is of course that all that debt that has been added over the years has been a huge contributor to that GDP. The fear is that the debt has just pulled a lot of consumption forward rather than infrastructure or other long term investments that will provide future growth opportunities.

Who is this debt owed to?  I presume most of it is just owed to other Americans.  The current account deficit represents the additional debt that is owed abroad.  Nevertheless, increasing credit tends to increase GDP and if that credit was spent on productive investment that makes the country more productive, then it will be easy to unwind the increase in debt.  If not, well...
The mortgage debt is a far bigger deal than the other debt because it is on a much bigger scale.  They should be graphed on the same scale and then it would be clearer.

Overcoming America's Debt Overhang: The Case for Inflation | The New America Foundation

Overcoming America's Debt Overhang: The Case for Inflation | The New America Foundation: "It might be called the 'World's Scariest Chart.' It is a snapshot of the fragile foundations of the American economy and the epic boulder it now finds itself trapped beneath. The graph shows total debt outstanding in the United States, both secured and unsecured, as a percentage of GDP. In 1981 it was a manageable 168 percent, in 1996 253 percent, and by the first quarter of 2009 with the collapse of the housing and credit bubbles it had reached a staggering 373 percent of GDP."

From Financial Crisis to Debt Crisis?

From Financial Crisis to Debt Crisis? By Kenneth Rogoff:

"For better or for worse, the reason most investors are now much more confident than they were a few months ago is that governments around the world have cast a vast safety net under much of the financial system.

At the same time, they have propped up economies by running massive deficits, while central banks have cut interest rates nearly to zero.

But can blanket government largesse be the final answer? Government backstops work because taxpayers have deep pockets, but no pocket is bottomless.

And when governments, particularly large ones, get into trouble, there is no backstop. With government debt levels around the world reaching heights usually seen only after wars, it is obvious that the current strategy is not sustainable."

What is the danger to the US of a debt crisis?  What would probably happen to interest rates, exchange rates, net exports (NX), inflation, and investment (I)?