The direct investment abroad makes a huge killing for the U.S. as can be seen from the balance of payments. In 2011, direct investment receipts was around $480bn and direct investment payments only $159bn.Read it at The Case of Concerted Action
U.S. Net Indebtedness Above $5T Now
Demand leakage in the US to external saving in dollars has resulted in an add to unemployment in addition to that resulting from debtor and consumer deleveraging owing to the balance sheet recession.
At the same time, US multinationals have been raking in money abroad through their investments there.
Whether or not it is sustainable economically, I doubt it is sustainable politically.
BTW, during his campaign trip to Iowa this week, Biden was going after Romney big on this.