[AnimalMuppet]

Could the NSA do this? Almost certainly.

Could they make it look like China was at fault? Also almost certainly.

Would they? Well, they'd need a good reason. What would a good reason be? To hone their attack skills? Perhaps. (I would expect - though I have no proof - that many of the American pieces of internet-critical infrastructure are more hardened against attacks than many other countries' stuff, because the American stuff gets actual attacks more often. If the NSA can attack our stuff to the point of breaking, it can probably break other countries' stuff.)

Would the NSA do it to hone peoples' defensive capabilities? To show them what a real nation-state attack might look like? Also perhaps. (Or perhaps it could even have both goals.)

Would the NSA be in very deep trouble if they ever got caught at that game? Probably. Deep enough to get them to not do it? I don't know.

TL;DR: The NSA could be doing this. I'm unsure how probable I consider that option.