Most people would assume that Trump has already done a lot of things that would make it harder for North Korea not to seek the aid of the United States, but it seems that he is more active on Twitter is trying to taunt Kim Jong Un. He did make a few changes, like trying to make other countries limit their diplomatic relations with North Korea.
He also made it possible for the sanctions for North Korea to become heavier as compared to before. Just recently, he decided that he would be meeting with the North Korean leader once again, and time will tell if anything good or bad will happen because of the next meeting.
With a couple of small exceptions Donald Trump has not really changed US policy on North Korea. He did sign an executive order to sanction companies that finance trade with North Korea. He also directed Nikki Haley to talk with the United Nations Security Council to impose new and stricter sanctions on North Korea.
He has also put pressure on other countries to restrict their diplomatic activities and several countries have expelled their North Korean ambassadors. But for the most part, Trump has only stooped to new lows for a President by using Twitter to bully and provoke Kim Jong Un by calling him a “sick puppy”, “lil’ rocket man” and “short and fat”.