The comments above criticizing Bernanke's paper focus on the fact that direct physical investment in assets in the United States do not offset the current account deficit.  But that is not what Bernanke says.  He says that the current account deficit must be offset by a capital account surplus.  But the capital account includes much more than capital expenditures to productive capital stock.  There are many spots on the Web, including Wikipedia which define the makeup of the capital account, but here is one I was recently reading from tutor2u^TM
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Economics Revision Focus: 2004
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Trade Deficit and Current Account

The capital account is one of two primary components of the balance of payments. It tracks the movement of funds for investments and loans into and out of a country.
The capital account is the net result of public and private international investment flowing in and out of a country. This includes foreign direct investment, plus changes in holdings of stocks, bonds, loans, bank accounts, and currencies.
The capital account only keeps track of the money being transferred (i.e., the worth of stocks is not taken into account as money when calculating figures for the capital account). Hence, a surplus in the capital account amounts to debtor status.
Along with transactions pertaining to non-financial and non-produced assets, the capital account may also include debt forgiveness, the transfer of goods and financial assets by migrants leaving or entering a country, the transfer of ownership on fixed assets, the transfer of funds received to the sale or acquisition of fixed assets, gift and inheritance taxes, death levies, patents, copyrights, royalties, and uninsured damage to fixed assets.

In fact note from the Bernanke article that I referenced, his own comment on one aspect of other countries investing in US Treasury Bonds:

In practice, these countries increased reserves through the expedient of issuing debt to their citizens, thereby mobilizing domestic saving, and then using the proceeds to buy U.S. Treasury securities and other assets.

I think this misunderstanding is leading many to miss Bernanke's point, which I have found to be a very insightful one.  It's not just the spending side of International trade flows that determines the entire picuture.  Decisions are being made on the investment side as well, and these decisions are just as influential as the spending side, perhaps moreso in today's worldwide financial situation.  Ignoring that will lead to an incomplete understanding of the world financial picture, and perhaps to less than satisfactory investment decisions.

I would be interested if anyone has seen a professional economist challenge Bernanke's views presented in this paper from May of 2005.  I have not found such a criticism, and am in fact under the impression that most leading economists agree with his views.  But of course I could be wrong, and would love to see such a paper.