Re: Pugwash 2.0?
You are (mostly) told incorrectly.
Normal process is for the President to sign a treaty then Congress to ratify it. Historically we have allowed the President to honor the treaty in the time between signing and ratification.
But as we recently learned, if a President stalls ratification so they can pretend it is a valid treaty, then a new President is elected, the new President gains the power to say "nevermind" because it was never ratified.
Had the process flowed as designed, ratified treaties cannot be abrogated by a new President.
The entire process is built around the idea that one person not have the power to commit the US to treaties or to break them. It was abused, and it backfired.