There is no such thing as a binding 'agreement' like this in the USA system of government. We have treaties. That have to be ratified by the Senate. The governments of the world understood this, and understood that the Paris climate agreement was an attempt by the US executive branch at the time to bluff to a hollow 'deal' (instead of creating a true binding treaty) hoping future politicians would be too embarrassed to go against it. It was incredibly disingenuous/misleading of the United States Executive branch at the time to do play politics this way outside of the actual US system of treaties. It was part of the breaking of American laws/norms by the executive that led us to where we are today (with chaos, tribalism instead of a legal system, and a breakdown of our government).