Keep these things in mind: It's not a treaty. It's never been ratified by the Senate or even submitted for ratification. It's got some legal standing in the sense that Congress failed in its "resolution of disapproval," which was Bob Corker's gift to Obama and the mad mullahs. But it's still little more than an executive agreement between Obama and his pals in Tehran, and Trump is in no way bound by it.
But Iran's President Hassan Rouhani seems to think he can somehow prevent Donald Trump from ripping it up - or at the very least, he thinks he can bluster about consequences enough that Trump will get nervous and back down: