Left Flank

Cato Institute's Doug Bandow (via TMH) is just not minimalist enough about his reasons for reforming the ROK-US alliance:

There's still good reason for positive relations between Washington and the South. Cultural, family, and economic ties all remain strong. Implementing a free trade agreement would help enhance the latter.

The military alliance, in contrast, is no longer relevant, having been created for a different geopolitical purpose in a different geopolitical time. Happily for both the U.S. and South Korea, the good guys won the Cold War. Neither China nor Russia would back the North in a new war, and the ROK is capable of deploying whatever size military that it deems necessary to deter potential DPRK aggression.

There are no good secondary uses for the troops now stationed on the Korean peninsula. Most of the subregional squabbles within East Asia aren't of much concern to America; Washington's other friends and allies, like South Korea, are capable of defending their own interests.

Most important, Seoul isn't going to join an anti-China coalition. Any American attempt to «contain» Beijing is likely to founder on the ROK's unwillingness to turn its behemoth neighbor into a permanent enemy. Indeed, China already trades more with South Korea than does the U.S. American domination inevitably will ebb.

The last resort for alliance defenders is to claim that ending the relationship would embolden the North. But Washington has begun negotiations with Pyongyang over establishing diplomatic relations; an American withdrawal could become an important bargaining chip.

I agree a narrowly-defined security alliance based on the DPRK threat is thin stuff for American generosity, for a multilateral swipe at alliances in general, Rajan Menon argues that «...that permanent security institutions are obsolete and the United States should pick up its military toys and go home.» According to another review:

The dissolution of our alliances will not, Menon emphasizes, culminate in isolationism. The United States will, and must, be actively involved beyond its borders, but by relying on contingent alignments and on coalitions whose membership will vary depending on the issue at hand. America, he reminds us, engaged the world in a variety of ways for more than 150 years before entering into formal military alliances after World War II. While a strategy that ceases to rely on alliances will mark a dramatic shift in American foreign policy, states routinely reassess and reorient their strategies. The United States, which studiously avoided alliances for much of its history only to embrace them during the Cold War, is no exception.

But, this sort of hairshirtness is not prudent, according to a review of Daniel D. Drezner's All Politics is Global: Explaining International Regulatory Regimes:

Unlike Mr Menon, however, Mr Drezner does not call for the end of such international accords. Rather, he finds that the challenges of the future will be increasingly transnational. As globalisation intensifies, the rewards for co-ordination will increase as well. To achieve success, it is essential not to eliminate international institutions but rather to understand their utility. They are at heart a means for great nations to exert their will in concert. The key to their success lies in convincing the leading governments of the gains from acting in co-operation, rather than isolation, in a volatile but interconnected world—a message that surely applies well beyond the esoteric world of trade regulations.

Choosing between empire or republic, it's doubtful the US can regain its republican virtue. It behooves America, with the last dying gasps of its moral promise, to bequeath the world something more beneficial than Yankee sport and the Iraq War debacle. A revamped trilateral, Japan-ROK-US alliance can persuade the PRC to reform its domestic institutions and its security relations, and a institutionalized defense pact in East Asia will ensure security and prosperity. Those who neglect political economy or refuse to look beyond bilateral arrangements make it harder for themselves. There's no such thing as a loner, and such states are a burden on the rest. America should at least do good to compensate for its brief bout of fractiousness and selfishness.