Your professor definitely has a point, as it’s been shown time and time again that whenever people of sovereign nations try to choose their own path for their country instead of a path that benefits the U.S., they immediately try to bring them back to their side through any means necessary (especially through Machiavellian ones). Just look at what happened to Iraq, or Libya, or Cuba, or Indonesia, or Vietnam, or even what’s happening to China right now. However, something I’d like to critique in your analysis is that Trump had never made a genuine effort to establish a decent relationship with Kim, given the fact that he had threatened him with nukes without provocation.
https://www.theguardian.com/us-news/2018/jan/03/donald-trump-boasts-nuclear-button-bigger-kim-jong-un
Btw, if you haven’t already, I suggest you check out this documentary since it looks like something you’d be interested in: https://youtu.be/7x5dH49s30o
Sure, it’s definitely quite lengthy, but there are timestamps for parts that might interest you in particular, and it’s genuinely something great if you want to see the other side of the DPRK that were never shown in MSM.