>My question is what purpose it would solve. By the time the route is finished, there won't be any way for the US to import anything from China. Food exports from USA to China, perhaps, as an attempt to pay the interest on what is owed?
Your post displays a lack of knowledge of how the trade deficit works.
In a nutshell, we don't borrow money from China. We buy goods and services from China, and we use US Dollars for the transaction.
China can then spend those US dollars in the American economy - perhaps to buy American goods in exchange - but they choose instead to put those greenbacks into US treasuries, which is the single safest investment in the world. Other countries would sell those greenbacks on the currency markets to obtain their native currencies, causing currency prices to fluctuate accordingly, but China has decided to keep their exchange rates at artificial levels that advantage them and disadvantage the rest of the world, especially the United States. But I digress.
The US treasuries that China owns can't be all called in at once. They can be sold on the open market, which technically could cause US treasury rates to rise, making borrowing more expensive for the United States, but in all likelihood they would not impact those rates by very much. The important thing here is that China can't roll up to the US Treasury with a briefcase (well, okay - trucks) full of bonds that haven't matured yet and expect to cash in. It doesn't work that way. While the US does pay interest on those treasuries, the interest rates are quite low right now.
There's a lot more to this - but suffice to say, macroeconomics is not microeconomics - things you need to take care of at a household level often don't mesh with what governments have to do in order to keep the books balanced. It's a common misconception that the US national debt is necessarily a bad thing.
