Earlier quoted context omitted.
I mean, I personally think its reasonable that the USA blew up the pipeline. Personally I'm at about 75% USA, 20% Russia, 5% someone else. I just also believe that Hersh's article was really, really, incredibly bad.
I haven't followed any of this really at all, but is there a compelling reason why Ukraine isn't at the top of everyone's list? Seems like they would have the motive to prevent Germany from giving-in to Russian demands to keep gas flowing and at the same time hurt Russia. It doesn't seem like it was a highly technical or expensive operation that would have prevented a smaller player from accomplishing it, and in fact…
a) it seems kinda implausible they have ability to blow up the pipe-line, nevermind to do so without being detected in what has to be the most cloesly monitored body of water on the planet.
b) Germany was already backing them. Blowing up the pipeline might make Germany marginally less likely to backslide, but if Ukraine were caught blowing up the pipeline, Germany would almost certainly turn against them. The risk/reward doesn't really make sense.
(FWIW, I think the most likely suspect is the one that doesn't usually get mentioned, that Germany blew it up to demonstrate their resolve regarding Russian sanctions).