Quick thoughts:

Transaction cost of bargaining/negotiation rise dramatically when you move from 2 parties to 3+. This will make many of the geopolitical conflicts brewing on the horizon more difficult to resolve peacefully/efficiently. esp. the north-east african water conflict, and the caspian sea oil issues. And trying to get Saudi Arabia, Iran, Turkey, Syria, Jordan, et. al to cooperate on Iraq's future, espcially without large potential cost (risk) of interference by the US (diminished both in potential due to low political support for middle east troop deployments, and in expected realized cost should it happen, due to demonstration that the us army isn't all powerful vs. guerrillas.)

Expand: has microeconomic analysis been applied directly to geo-politics broadly, to encompass more than just trade disputes? (I think game theory has been towards and understand of the cold war).