Victor Davis Hanson presents an honest, well-reasoned prescription for dealing with all the carping from our erstwhile allies -- Pull Out. 

...there is "teenager disease" — the notion that through our predominant military strength and omnipresence in Europe we have become resented and parental. The young rant and rave at their stronger benefactors as expressions of angst over their dependence, both psychic and material. Allowing the Europeans to chart their own course in matters of security would be healthy for both parties — as overprotective mother and fathers are quick to learn when their twentysomething offspring finally moves out.

...Germany finds it can turn on its traditional patron precisely because we have so many Americans within its borders, and seem so intent on keeping them there at all costs. We claim we are there to create stability; they counter that we merely use their bases as transit centers to facilitate mischief abroad.

American power projection - as Afghanistan so beautifully proved - is increasingly no longer a question of men stationed as on the ground deterrence.   And, as VDH dutifully notes, in an era where even a single American serviceman casualty makes a political statement, the prospect of 37,000 soldiers in S. Korea makes Kim Il Jong drool, not cower in fear.  

Full global retrenchment, of course, is neither feasible nor recommended.   We do however, have the ability to do (or at least credibly threaten) a net pull out to call our allies bluff.