It is, as usual, irrelevant.
The US will pursue policies that mean that the home economy will not be affected. If the US stood to gain by reducing it's emissions, it would sign the treaty.
Vested interests, short term gain, and the externality of future generations that have no vote in what we do to their situation and environment.
For nemt: (although banging one's head a brick wall here
) try reading this article,
from the New Scientist. and the various weblinks at the right hand side for links to the wealth of articles and information from the UN and other research institutes. Of course, you will probably argue that Nobel Laureates are mis-informed because Fox news told you otherwise
but more clear thinking folks might find the evidence more compelling than that which has been commissioned in support of the official US position.