Well, I’m not sure if you have shifted in your opinion from only entertaining the bombings must have been carried out by the Russians (as I recall).
But if you now do consider the possibility that the bombings may have been carried out by the US, there is one more question to consider. Would those planning to carry out the pipe bombings consider the damage inflicted on Germany as collateral damage as a result of inflicting a blow to Russia or as something desirable.