Russia had already shut off the gas, "hurting" themselves by your own logic. They have a long, proven history of irrational behaviour and false flag operations. And if the USA had done it, against all reason and logic, why didn't they finish the job?

Anyway, I did say almost certainly Russia. Who knows, could have been some faction in Germany or another EU power seeking to really force Germany's hand. But it seems far more likely to be the obvious actor with the means, motive and mindset who started the bloody war in the first place.