Right-wing extremist senators are pushing the wrecker to submit the Paris agreement and the non-nuclear deal with Iran to the Senate as treaties, the idea being that the Senate will reject them and then Biden would somehow be unable to reenter the US in them.

I am skeptical that this would deal a mortal blow to US participation in those agreements — simply because officially approving them is not crucial to making them effective.

What Iran wants is for the US to drop sanctions. If the president drops sanction against Iran, Iran will comply with its side of the deal. Whether the US continues in that policy is a political question, as the wrecker has already shown. So Biden can drop the sanctions, and Iran can limit its uranium enrichment, even if the deal is not official.

As for the Paris agreement, all it does is require the US to make a weak pledge to reduce emissions. Biden can do that even if the US can't officially rejoin the Paris agreement.

However, survival requires the US to do a lot more than that. So let's focus on getting a policy that meets the physical world criterion.