But is a growing economy necessarily healthy? Is a growing economy the only measure of the overall health of a nation, economic or otherwise?

I understand that 2/3 of the US GDP is due to consumer spending. Wouldn't take much of a wobble there to send things into a tailspin.

Also, how much of the US national debt is held by China and Japan?

Check out this site

this one

and Wikipedia, which says:

U.S. public debt
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The U.S. public debt, commonly called the national debt or the gross federal debt, is the amount of money owed by the United States federal government. This does not include the money owed by states, corporations, or individuals. As of December 2005, the total government debt is approximately $8.1 trillion, i.e. $8,100,000,000,000 ($8.1 × 1012). This is more than ten times the amount of United States currency in circulation as of 2005, estimated to be $730 billion ($7.3 × 1011). The debt can also be measured as a fraction of the nation's gross domestic product (GDP); at present, U.S. public debt is about 65% of the GDP, a rather average level when compared to other nations.

In several cities around the United States, but most famously at Times Square in New York City, there are national debt clocks—electronic billboards which supposedly show the amount of money owed by the government. Some also attempt to show the money owed per capita or per family. A division of the United States Treasury Department known as the Bureau of the Public Debt calculates the amount of money owed by the national government on a daily basis. There is a significant level of fluctuation day-to-day, both up and down, so any "clocks" must be continually re-set with proper values.

Contents [hide]
1 Structure of the debt
2 Calculating the debt
3 Projecting the future debt
4 Paying the debt
5 Risks
6 A brief history of the debt
7 See also
8 External links
9 References

[edit]
Structure of the debt
The Bureau of the Public Debt divides the national debt into two main categories: debt held by the public, and intragovernmental holdings. Intragovernmental debt includes money for government trust funds, such as pension plans and the debt for social security which is about $1.7 trillion as of May 2005. Overall, intragovernmental holdings account for over $3.1 trillion of the total debt at this time.

The remaining $4.6 trillion or so has been purchased by the public, including foreign entities. This largely comes from the issuance of US Treasury securities. Nearly half ($2.2 trillion) is composed of Treasury notes (aka T-notes), while T-bills and T-bonds (including savings bonds) cover most of the remaining public portion of the debt. Bonds sold for infrastructure projects are also part of the national debt.

It is common for individual Americans and businesses to buy bonds and other securities, though much of the debt is now held overseas. At the end of 2004, foreign holdings of Treasury debt were $1,886 billion, which was 44 percent of the total debt held by the public. Foreign central banks owned 64 percent of the Federal debt held by foreign residents; private investors owned nearly all the rest (figures are from the Analytical Perspectives of the 2006 U.S. Budget, page 257

The country holding by far the most debt is Japan which held $1.2 trillion at the end of March, 2005. In recent years the People's Republic of China has also become a major holder of Treasury debt, holding $223.5 billion at that time.