The British

"The Americans are at war, the British are on operations."

http://www.economist.com/world/britain/displaystory.cfm?story_id=13022177

Most foreign militaries are fighting a war of discipline, rather than a war of survival.  The US is unique in its ability to wage such conflicts (we LOVE violence, wherever the idea came from that Americans have a weak stomach for conflict, that idea has been proven wrong over and over again.)  But there are countries for whom this IS a war of survival and whom we haven't yet tapped as a potential source of military capability.  China and Russia both need the US to do well in Iraq and Afghanistan, and to prevent the rise of a hostile Iran.  Pakistan and India have far more important contributions they can make than staring at each other across Kashmir.

In the mean time, the British military is having difficulty adapting, not as much from a lack of ingenuity as issues with institutionalism and budgeting that we have had an easier time overcoming.