My guess is noting more than embarrassment, if the situation of non-execution still holds true. US government action in the form of trade sanctions will kick in. The other nations will have to adapt, and they will continue to complain.
It's possible the agreement is litigated in some world court, but I doubt it. JCPOA is a political reality, even if it was not formally executed. Does Iran get to pull out if say France pulled out? Who are the essential parties?
Iran is not in, they’ve never been in. They never ratified it, it never went to their president to sign it. They laughed about it when they agreed not to sign it. And they never honored it. What it amounts to is a unilateral, arbitrary removal of sanctions by one Barak Hussain 0-bama. Only think I can’t figure out is why he made the profound bow to the Saudi King when he was on the side of the Shi’a all the way. Or maybe he was playing both sides.