Could have been the Paris Climate Accord (I loved Trump for just pulling the plug on that) or the Intermediate-Range Nuclear Forces (INF) Treaty which was a real treaty (I think) that we had proof the Russians were violating. When they refused to provide concrete information proving they were in compliance, that met the requirement for a withdrawal and Trump did it.
That is why we supported him. He DID things that SHOULD have been done.
it mighta been that- i cna’t recall now