The main problem with Clinton's argument is that there is no particular connection between the amount of U.S. debt that China and Japan hold and what happened last week. Is she really saying that the U.S. market wouldn't have dropped after the Chinese market dropped if we ran a trade surplus with China? Or if we still ran a deficit but China's resulting portfolio holdings were in some other country's federal liabilities rather than ours? Our economy is connected to the Chinese economy via both current account and capital account transactions. We might want to be more mindful of the latter than we have been. But that doesn't mean that the high ownership of U.S. debt by China caused the transmission of price movements from China to the United States.
Read this excerpt and see if she actually justifies the leap she makes in going from the red to the blue sentences below:
I have long argued that a great source of vulnerability is the fact that other countries, including China, own so much of our debt. Today, foreign nations according to the most recent Treasury statistics hold over $2.2 trillion or 44% of all publicly held United States (U.S.) debt with Japan and China alone holding nearly $1 trillion. In essence, 16% of our entire economy is being loaned to us by the Central Banks of other nations. Having so much debt owned by other countries can be economically unsound. Yesterday it was the sell off of foreign stocks that had reverberations in U.S. markets. But if China or Japan made a decision to decrease their massive holdings of U.S. dollars, there could be a currency crisis and the U.S. would have to raise interest rates and invite conditions for a recession. While it can and will be debated whether yesterday's market disruption was just a blip or a larger indicator of our economy's vulnerabilities, it is clear that interdependence between our economy and that of other nations can pose a risk if we do not pursue smart policies. Precipitous decisions by any country with our debt could create much graver economic problems than what we saw yesterday. The writing may not be on the wall, but yesterday, the writing was on the Big Board.
Her "in essence" sentence is not a sensible comparison. It does not make sense to compare a stock of money--the total holdings of U.S. federal debt by foreign investors--with the flow of money that is U.S. GDP. A sensible comparison might be the flow of interest that we pay to these foreign investors, a much smaller number as a share of GDP. (For example, I don't get too worried about the fact that a bank has lent me more than 100% of my income in the form of a mortgage. The reason is that the interest on that mortgage is a very reasonable fraction of my income.)
The statement in green above is a true statement. Not only would the problems be more grave--they might actually be problems and be related to what the creditor nations did. But even this scenario that she discusses is, in Mankiw's word, alarmist. There would have to be a reason why China or Japan would intentionally precipitate a selloff of their holdings of U.S. debt, particularly since the Chinese and Japanese holders of the debt would be the first ones to suffer the capital loss due to this action. It couldn't simply be that their own economies faltered--the U.S. debt they hold is an asset to them. When my income falters, I am typically quite grateful for the assets I have in the bank (somebody else's liabilities). Their economies would have to falter so badly that they needed to liquidate their holdings of U.S. debt to pay off some of their own debts. Not too likely, unless, perhaps, we close our markets to them.
Clinton's rhetoric, particularly these statements about being "held hostage" or "losing our economic sovereignty," suggest that she's thinking about a scenario in which a policy maker in Beijing or Tokyo decides that the U.S. debt is overvalued and wants to unload it en masse. About the only thing that could really convince me to do this, were I the policy maker in Beijing, is a credible belief that my counterpart in Tokyo was about to do the same thing.
While that is something over which Washington has very little control, even in that case, all that would happen--unless you think the U.S. government wouldn't pay the interest or principal on its obligations--is that the U.S. dollar would depreciate and domestic interest rates would rise. Exports would pick up a bit, and the government would find deficits more costly to finance. I'd prefer if that didn't happen, but in the grand scheme of things, it's neither very likely to happen nor very severe in its real consequences if it does.