Given that Biden has explicitly threatened to sabotage the NS2 pipeline, it's not I would say that the prime suspect has to be the USA. It's true that Russia would be the secondary suspect, just because of their quite erratic behavior.

But it is extremely important to note that Russia always had the option of simply stopping gas delivery even if the pipeline was not destroyed (and Germany similarly could stop delivery at the other end), while other parties had to actually sabotage the pipeline if they wanted to prevent such deals.