You are right, I was overemphasizing the role the USA had in destroying an agreement the world signed onto (and watering down all subsequent agreements), and in doing so I undervalued the role of the largest historic polluter has in actually lowering emissions.
Thanks for the follow up -- it's frustrating to not reach consensus when you think you're right (and yes, I'm prepared to be wrong if the argument is persuasive enough).
But for the sacrifices and investments required, it's ludicrous to say "this needs to be done" and not actually do it.