@ Satai, NobodySpecial,
The reason might just be that the US and China are the only ones "caught with their pants down" as it were...
The US for some reason has been talking up China APT for some time now and at the same time stiring it up between South and North Korea.
Has China / North Korea been doing APT well yes the evidence does kind of look that way. For instance various new Chinese fighter aircraft have more than a passing resemblance to the latest US fighters and prototypes (the joke being it appears China got of the drawing board faster, so possibly it's the other way around ;)
We know that France's "secret service" regularly performs espionage of all forms on forign companies as a routien matter and has actually said so in public. The British are supposadly famous for saying nothing unless it's about "fairy Cake Recipies" disguised as PDF files. All major EU powers spy on each other and other nations as a matter of standard operating procedure. Likewise a number of "Comenwealth Countries" (go look up BRUSA agreement) it's just it does not get talked about because it's not realy in anyones interest to make a lot of noise about it.
We further know that all major Western powers spy on each other and occasionaly let each other know when they detect attacks from "outside the club". For example when an APT drop of point was discovered various IP addresses were back tracked to "Other Nations GO's" and a "word to the wise" given.
We also know that Israel are at it at all levels which is why some of their "employees" are currently undergoing an unpleasant time in South Korea (basicaly S.K regards industrial espionage up with spying on the mil/Gov or treason and have some hefty punishments awaiting).
As normal it's the "fear factor" that's bringing China and the US into the spot light. Realisticaly the US and China have been fighting "proxie wars" since the end of WWII but China has not been the aggressor unless the US "craps on their doorstep" an example being Taiwan. In the Past China would hold war games or send down a submarine to cut an undersea cable to make a point and it would all settle down again.
However China started changing the game plan and in many respects have made a lot of people in the US very nervous, especailly the way China has bought up US assets one way or another. This has reached the point where the US is tied into China in a way that makes dirrect conflict very improbable as China has a very significant economic leaver to lean on when required.
Thus economic warfare is where the next conflict is likely to happen and China is way more likely to survive that sort of conflict than the US (which is very much on the ropes economicaly with only the use of the US Dollar as the international trading currency keeping the US nose above water).
The fear is the US war Hawks will get their way and it will switch from economic to bombs and bullets warfare and the trigger may well be the prolific use of Cyber Espionage that appears to originate in China. The evidence is collecting but it could be others working through China or various factions within China fighting it out. Either way China has been making some interesting noises in resolving some of the issues if this is genuine or just delaying tactics is unclear and is likely to remain so.
However if genuine it is going to meet some fairly stiff oposition in the US in certain quaters as various people have advanced their positions considerably of the back of "China APT" and now they are within an inch or two of getting "the keys to the sweetshop" they are not going to give up without a fight.
As the old Chines curse has it, we now do "live in interesting times" the question is where do China/US go and what do they do next...