Are you actually trying to argue with me, or just taking a potshot at the USG? If the latter, please use someone else's comment as a platform and not mine. If the former . . .
Sheer pointlessness is meant to encompass several reasons I believe the USG is an unlikely culprit.
First, there's the risk of significant consequences if the USG's involvement comes to public light. There's another election in two years, so even the PR damage could cost them. Then there's the matter of this kind of action being illegal. Maybe no prosecution would occur, but maybe it would.
Second, unlike your security theater example, there is literally zero chance of this doing any good for anyone. Every person who is even the least bit interested could obtain the documents with only minor effort considering how widely they have been distributed. Major news organizations have already collated them for the masses.
On the other hand, "security theater" and "unwinnable wars" are only pointless in a debatable sense. There are obviously a large number of people who believe that airport security measures are having some positive effect. Similarly, by some metrics (not mine), the war in Iraq has been successful and the war in Afghanistan is heading in that direction too. I don't doubt in hindsight that they will prove to be mistakes, but that is not the same as their having a absolutely known "pointlessness" value now. So I think that objection of yours is incorrect as well.
Also, you've only pointed out two pointless things the USG has done in the past decade. That's not the same as proving that the USG is equally inclined to do pointless things as pointful ones. In fact, it may be that the USG discards pointless courses of action at a much higher rate than pointful ones, but that certain pointless actions have been enacted nonetheless. In this case, it would still be predictive of the US not being involved that the Wikileaks DOS is pointless.
Finally, I'm not aware that it is the USG's standard infosec policy to maintain batteries of compromised civilian computers with which to perform cyber warfare. Perhaps it is, but that would be quite a discovery in and of itself.
So, there are a lot of problems with your line of reasoning. I could be wrong, but I think the odds are something like 80-20 that I am right and this is not the USG's doing.