This isn't insanity. On the contrary, this is compellingly rational. DT is pulling America out of the global hegemony game and reinforcing its status as the dominant power of the American hemisphere. More specifically, he is pulling out of Europe and fortifying the American position at home (hence Venezuela and Greenland). He is NOT, however, pulling out of the Middle East and the Western Pacific, indicating that those are far more vital interests to the US than Europe.
Agreed. Just securing western hemisphere already gives him a lot of leverage in terms of oil/minerals producing region that China depends on. Add that with US's grasp on Middle East. I'd say he intend to be able to choke off China's industry when the time come. We shouldn't underestimate him or his backers.