I live in Australia, if American troops pull out then what is stopping China from just taking the South China Sea. China has proven it doesn't care about international law as demonstrated by the Hague ruling. If Trump pulls out China is going to bully it's way into getting what it wants, which will most likely start a war, we need to keep the counter-balence that is American troops. The world never did anything when Hitler invaded Poland, they only acted when after Hitler had gained so much power. If the world responded right after Poland the war could have been years shorter and tens of thousands of lives saved.
Think about it, Hillary is very aggressive towards the Russians and the Chinese. She wants to establish a no-fly zone over Syria to stop Russia from bombing Aleppo. Many current and retired US military generals and pilots say that if this no-fly zone proposal goes through then it could lead to a military confrontation with Russian aircraft and potentially lead to a war. Hillary is also aggressive towards China and its policies in the south china sea.
Trump on the other hand, plans to pull US troops out of Asia and he is friendly with the Russians. Trump won't start a war, Hillary will