There's also the matter of "is this worth starting a war over?"
One thing about this is that Chinese military is not the same thing as Chinese intelligence. The main Chinese intelligence agency is the Ministry of State Security. Mixing up the PLA with the MSS is like mixing up the DOD with the CIA.
I doubt that the United States government will do anything more than "raise the issue." The trouble is that if the US does something like file a formal diplomatic protest, it will be a promise by the United States not to try to do anything similar, and I don't see how the US would consider that to be in its national interest.
One other interesting thing is that the Chinese hacker community is very different from the US hacker community, in that US hackers tend to hate the military and authoritarian systems whereas the Chinese hacker community sees themselves as patriotic defenders of the motherland. A lot of this has to do with differences in history (i.e. the US involvement with Vietnam). Something that gives you an idea of the difference is that if you go to any newsstand, you'll see a lot of military magazines, and so hackers in China are "solider wannabees" in ways that hackers in the US aren't.