The USA is big, but China bigger. If the USA over optimizes on reducing greenhouse gas today, at the expense of our long term economic and world power, China, who cares for less about preserving the world will continue to destroy the world and claim the most power simultaneously.
So while we can reduce OUR footprint by taking ourselves out of the game, the world still loses.
So now try to find a less myopic solution where we remain powerful enough to get the whole world to tamper down their impacts.
We don't win by removing ourselves from the competition. And the competition has a high chance of killing us all. But rolling over is a guaranteed way to lose everything everywhere.
Oh and the prior commitments like the Paris accord were engineered to harm us while allowing China to dominate.