At present, the US is putting pressure on the DPRK and Iran regarding nuclear issues at the same time.
Will Trump’s withdrawal from the Iran deal set a very negative example for denuclearization on the Korean Peninsula?
There are many ways to interpreted it. On one hand there is the idea that violation of the JCPOA shows that the USA cannot be trusted to uphold its agreements. On the other it establishes Trump’s credibility as a hardliner not afraid to take action. Uncertain how North Korea will ultimately perceive these issues. Trump may make clear that JCPOA was only an executive agreement in the USA, and was never ratified by the Senate as a Treaty. Trump may propose to North Korea that any agreement must be ratified by USA senate as a Treaty. If North Korea believes it is able to secure a lasting agreement in form of Treaty, example of JCPOA only underscores the importance of reaching an enforceable deal.