If we don’t want to lose key military bases and shipping routes in the region then we should continue to honor our treaties with Japan and South Korea. Our treaty with Japan also sought to to have them re-emerge as an economic ally as opposed to a potential military adversary. Through our treaty negotiations, we compelled them to include Article 9 in the Japanese constitution which states;
“The Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes.”
These are the remnants of the spoils from our WWII victory over Japan. In consideration of Japan’s limited military capabilities, we renegotiated treaty obligations in 1960 to form a permanent military and economic alliance with Japan. The revised treaty guaranteed Japan protected sea and air trade routes with the outside world in return for US military access to Japanese territory.
Essentially, our treaty alliance with South Korea establishes a similar, mutually beneficial alliance. I don’t believe it would be in our strategic interests to abandon either treaty without assurances that our military and trade access to the region will be maintained.