Lets talk about this. Why do we have military bases in foreign countries? What national interest are they protecting? Should the host country pay for the base? Should we close them unless the host country pays?
Why is it our role to protect South Korea and Japan from China?
Why is it our role to protect Germany from Russia?
We have a vested interest in having other free democracies on Earth. And as the leader of the free world ask yourself what is in our best interests and what should we be obliged to do?
To help others gain and maintain their freedom?
To help them stand up to Communism?
To help protect the supplies of oil to our trading partners?
To make sure that in any circumstances when a small revolt or insurrection might explode into something bigger and much worse that we would eventually have to solve when it was mush costlier to do in blood and treasure, having bases in those countries allows us a smart and less expensive way of preventing major problems we'd have to deal with later.