Who would they really be hurting in the long run though?
Say, 2 or 3 months, we can't get iPads, iPhones, or many other items. Is business in the US going to grind to a halt? Nope. Is business in China going to grind to a halt? You betcha.
However, factories will start sprouting up in the US again - products will be more expensive, definitely. Within a few more months, there will be locally made products. Don't forget that Intel's plants, and several memory makers are in USA - there's no reason they couldn't put up new plants very fast.
Worse will be the corporate-political fall out. If you could buy a widget from a local made factory for $100, and could pretty well guarantee delivery short of Force Majeure, would you buy that, or a Chinese made widget for $80, but supply could be stopped at any time? Right now, businesses see Chinese supply lines as stable. The Chinese government pulls a stunt like that, and it creates a sovereign risk - something it's been trying to avoid for decades now.
Your problem is that you're looking at US vs China as singular entities. The Chinese factories aren't holding US treasury bonds, the Chinese government is. Unless the government wants to just give out free money to all former employees and factory owners, then there's still going to be civil unrest.
But if we're talking about sovereign risk - who's to say that the US simply won't say "Had enough of these austerity measures. Had enough of debt ceilings. We're refusing to honour any outstanding treasury bonds." Why not? It's just as silly an idea as China putting an export embargo on itself.