It is economically nonsensical because it effectively assumes that US spending is all related to capital expenditures to productive capital stock (which is not true). Actually US capital expenditures (in last few years) related to productive stock are roughly equal to amount needed to keep it in current level (i.e. to stay afloat). The US current account decifit is mostly due excessive spending to consumption and residential (effectively non-productive as far as import/export is concerned) construction.
It is also good to remember that US is not terribly good in attracting foreign portfolio investment (US investments are larger to abroad than foreign investment to US) and large current account decifit is due foreigners putting their money into US debt instruments.
Thus the trade decifits and current account decifits are not due any great surge of capital investment to US as engine of World economy.
Here is some data to illustrate it:
US FDI flows 1995-2004
Home made with data from UNCTAD FDI Database Source: Bureau of Economic Analysis, U.S. Department of Commerce.
About the poor quality of the picture, please, be indulgent: it's the first time I use Photobucket to upload a graph I made... "Dieu se rit des hommes qui se plaignent des conséquences alors qu'ils en chérissent les causes" Jacques-Bénigne Bossuet
Thanks for the source on FDI. I've longed wanted such a source to build a graph with French inbound FDI compared to others, to show that despite its 'horrible' policies, it is an attractive place to invest in. In the long run, we're all dead. John Maynard Keynes
I've commented below to the effect that IMO your comment and others are defining the capital account in balance of payments as "capital expenditures to productive capital stock", in your words. The capital account in fact includes the US debt instruments that you mention above, as well as investment in securities.
