The US was caught when somebody blew the whistle, just Google for PRISM, for example. China and others could not have done that, therefore they would do something else. They make and ship hardware, therefore their vector of attack would be expected to be that hardware.
Unlike the US though, I am not aware of any substantial attack that goes beyond speculation. There was supposed to be an IC implemented into Apple and Amazon servers according to Bloomberg but that story was refuted and went nowhere.
So far, in reality, we have proven US surveillance(and Obama was very sorry about it) and speculations about Chinese surveillance.
I am not sure that there's much going on here beyond the propaganda.