> Also if Russia did do it, its officially an attack on NATO and requires a response?
In either the case of America attacking a pipeline jointly owned by the Russians or the Russians attacking a pipeline jointly owned by a NATO country, you could call this an act of war. But in neither case will either side use it as their casus belli to start WW3, because nobody wants that. Nobody is waiting for a 'legitimate' excuse to start such a war. It is much safer for everybody to pretend they haven't noticed such attacks, or to pretend that the culprit is uncertain or maybe that it was done by accident. Pretending to be ignorant of the provocation is preferable to WW3, for both sides of the conflict.
In either the case of America attacking a pipeline jointly owned by the Russians or the Russians attacking a pipeline jointly owned by a NATO country, you could call this an act of war. But in neither case will either side use it as their casus belli to start WW3, because nobody wants that. Nobody is waiting for a 'legitimate' excuse to start such a war. It is much safer for everybody to pretend they haven't noticed such attacks, or to pretend that the culprit is uncertain or maybe that it was done by accident. Pretending to be ignorant of the provocation is preferable to WW3, for both sides of the conflict.