[The Dems are continuing to undermine Trump, so that he doesn't have the political support to take timely and effective action against N. Korea.]
What are you on about?  Trump's first choice was to flip-flop on calling China a currency manipulator and relying on China to stop Kim Jong-Un's nuclear and missile programs.  This was obvious back in February.
http://www.cnn.com/2017/02/27/politics/china-us-north-korea/index.html
And carried on for over a month.
https://www.washingtonpost.com/news/worldviews/wp/2017/04/13/trump-thought-china-could-get-n-korea-to-comply-its-not-that-easy/
Then the Trump administration compounds the issue by presenting a divided, muddled approach with no firm goals in mind with Trump first saying, "We'll do everything" and Tillerson's "not your enemy."
As usual the problem with the Trump administration's foreign policy is with Trump's ham-handed approach.  It doesn't help any that the Moon admin in SK reversed, twice, on a missile defense system in SK.