There is a reason that Northeast Asia has been stable since the end of the Korean War after decades of conflict and that is the US military presence in the region.  Doug Bandow from the libertarian Cato Institute disagrees:

But that world disappeared long ago. The Korean Peninsula has lost its geopolitical significance, South Korea its helplessness, and America’s Korea commitment its purpose. While there is much to criticize in the approach of Donald Trump’s administration to the rest of the world, the president correctly sees the need for a foreign policy that more effectively protects America’s interests. A good place to start shifting course is the region home to the world’s newest and least responsible nuclear power.

The Koreas are no longer a proxy battleground between superpowers. There was a time when U.S. withdrawal from a confrontation with a Soviet ally in Asia would have, analysts believed, signaled weakness a continent away in Europe. But the Soviets are long gone and the cause for American commitment with them. An inter-Korean war would be tragic and the body count enormous, but absent American involvement the fighting would largely be confined to the peninsula. The continued presence of U.S. forces, by contrast, virtually guarantees the spread of conflict.

South Korea’s defense no longer requires Washington’s presence. The South’s economy began racing past its northern antagonist during the 1960s. Democracy arrived in the late 1980s. By the 1990s, when mass starvation stalked Pyongyang as Seoul’s economy boomed, the gap between the two Koreas was already huge and growing. The South’s military potential is correspondingly great though as yet unrealized — in part because dependence on the U.S. presence has affected strategic choices.  [Foreign Policy]

You can read the rest at the link as well as read my prior analysis of why USFK withdrawal will not happen any time soon at this link.