I don't think the US did this at all. But, I'm not sure I agree with the guy's reasoning that if the US did it, they wouldn't do it between the detection and attribution levels as was done.
I think that's only true if the US *looks like* they may be behind it, weakening resolve in Europe. Otherwise, sabotage between those levels serves the US interest in forcing Europe's hand by taking Russian gas off the table. That wouldn't necessarily be true *if* the US had done this below the detection threshold.
His point about a losing, desperate actor being much more willing to undertake such a risky operation is well taken, too.
I also agree that other non-Russian undersea assets may soon become targets (which points convincingly at Russia rather than any other actor).
"A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it." ~ Max Planck, 1950