US withdrawal from S. Korea and Japan will trigger nuclear arms development in those countries leading to Asian nuclear arma race, much like that between India and Pakistan. The purpose of using 30,000 US servicemen as essentially hostages in S. Korea is to assure the nations of S. Korea and Japan that they are under the US nuclear umbrella, thus obviating the need for nuclear Korea and Japan. It has been the standing policy of the UN permanent security council nations to prevent the spread of nuclear arms. US will not change 50-years of international policy direction at the whim of some unhinged loon. Pres. Trump, even if re-elected, has at most 2-years more of "governing." The US military and foreign offices are staffed by career bureaucrats with farther reaching vision than a reality tv conman. All S. Korea and Japan need do is prolong negotiations, until Trump gets bored, or is out of office.