The problem comes down to proving it.
If this was an attack, there would be perp footage which when combined with signal intelligence, cross referenced with data from inside CIA all but means perp names, origins, date of entry, murder weapon etc.
I'd agree that Americans would be on the top of the list to blame if the guy was killed while in a NATO country. But in order to attack someone inside China, you need hitmen to travel inside China first. The whole thing leaves paper trails.
Your counter was that such an assasination is easily traceable by the CPC and its intelligence organs, but I used Snowden's revelations and the Hong Kong Color Revolution as examples in which the CPC failed to catch and prevent US intelligence infiltration.
And as I explained, HK had issues because it was legal for other countries to send and hire agents there, prior to the NSL. If anyone can be blamed it is the lawmaker, it has nothing to do with intelligence capabilities. And as also explained, if China knew about US spying, they wouldn't blow it to US state media, they would just use the information. So Snowden being the "first" to blow something which more likely than not any major independent state agency knew doesn't say anything about intelligence capabilities.
While you are absolutely correct in the fact that paranoia can paralyze one's thinking process, I also believe that one should simulatenously think outside of the box and not dismiss things as accidents, particularly high profile ones. Crazy stunts pulled by intelligence agencies and their precursors are common in political history.
At the end of the day, I think we should agree to disagree and just wait and see.
I mean yeah if within soon^tm China just starts naming names and pestering US like UK was pestering Russia after the supposed Russian great novichok smearing incident, then that would mean something different.
If that's true, it would instantly put us on the verge of ww3. Not entirely impossible because flash points do happen in cold wars.
So I can agree to wait and see, but the fact China just publicizes this likely speaks to it being an internal matter of the undercover research teams.