you really knows nothing about financial, and world politics. Let me point out some thing:
1. Chinese government invests both in corporate bonds and US treasury bill. a big part of corporate bonds are in FRE and FNM. If FRE and FNM bankrupt, default on its bonds, Chinese government gets nothing back, just like current FRE and FNM's share holders, what can China do? Fire nuclear missile? send PLA? US government never guarantee 2F's bond in the writing, I would think if u were US president, u would be so happy that u tricked the whole world to believe that US government backs 2F's debt, but never write it down, now it is the perfect chance to default, right? we never forced those "stupid" Chinese to buy our bonds, right? But US changed corporate bonds into government bonds at crisis, Chinese government 松了一大口气, right?
2. When u buy bond, how can u demand issuer to return your principle at any time? if you can do that, why would people sell bonds? if no body sells bonds, how u get money to build rail way, free way, olympic buildings, ...? if u want your principle (money) back, u can sell your bond on the market, it is your freedom.
You are too ignorant for us to have meaningful conversation, I do not have that much time to teach u basic knowledge. please study more before u open your big mouth, now is not time of “知识越多越反动”