And because I read "listening in" literally, as intercepting audio, rather than metaphorically as being able to intercept all traffic.

Also, the US has blackmailed people, like the FBI attempt to blackmail Martin Luther King Jr. We know the US gathers the porn habits of people who it considers might be a threat, including of a US person (https://www.huffingtonpost.com/2013/11/26/nsa-porn-muslims_n... ).

So really it's a matter of balancing the odds. The odds are low that either government will care about me. It feels more likely that my life will be upended by a mistake, like what happened with Brandon Mayfield, and a mistake by the US government is far more likely to affect me than a mistake by the Chinese government.