On the face of it, Trump’s erratic behavior with allies and his violation of the 2015 accord on Iran’s civilian nuclear enrichment program ought to give North Korea pause about negotiating with him.
It does not.
The Iran deal in particular was closely negotiated over the course of years. Iran gave up 90% of its nuclear enrichment program in return for an end to economic sanctions. While the other member states of the UN Security Council did lift UNSC sanctions, the Republican-controlled Congress not only did not lift unilateral US sanctions but actually slapped more on.