Our country is in debt.  Very far in debt.  We're talking $9 trillion worth of debt!  Somebody has to own that debt and the Chinese government is more than willing.  In fact, they own about 80% of our nation's debt.  That's not only scary that a foreign government owns that much of us, but also a threat to national and economic security.  Hypothetical time...

Let say that relations with Taiwan and China deteriorate.  The United States has traditionally came to the defense, tacitly of course.  Let's say that we decide we're going to put our ships near the Taiwan Strait to "monitor" the situation.  This would obviously be seen as an aggressive move by China and they would no doubt retaleate some how to show that they were not happy about our ships.  What if they decided to stop buying our debt?  Our economy would grind to a halt as our credit line got cut off. 

Or, let's say we take a harder stand against Iran?  China might not like us placing further sanctions on Iran and may use economic pressure on the United States to make us rethink our strategy.

In light of these two "what ifs" and the FACT that China owns 80% of the United States debt only makes the raising of the Chinese flag at the White House that much more ironic and fitting.  Eventually, we're going to have to pay the piper, and the piper only takes yuan.