I'm not sure how up to date this professor is.  As a Canadian living in China, planning a trip to Korea, I follow this perhaps a little more closely than he does.

Firstly his comment " a reunified Korea would likely ally itself with China, as the strategic need for U.S. military presence in Korea would be eliminated" is a fairy tale.  Is he aware of the current tense relationship between China and South Korea?  China is having a hissy-fit over the deployment of the THAAD anti-missile system recently deployed in Korea and are using all kinds of childish means to show their displeasure.  The relationship between the two countries at present is very poor.  A combined Koreas won't be ruled by the north.

Secondly, the Carl Vinson isn't steaming towards Korea, it's already in the theatre.  Does the prof have any idea how fast a nuclear powered aircraft carrier can travel?