In the absence of a preeminent Soviet rival lurking over the European landmass, a weakened N.A.T.O., in the estimation of U.S. leaders, may ostensibly secure America’s hegemonic interests by derailing potential challenges to U.S. primacy. Hegemony, however, comes at a high cost. Attempts to retain it can even hasten hegemonic decline. Given the immediate threat facing NATO’s prestige in Afghanistan, as well as America’s soaring budget deficits at home, the current state of the trans-Atlantic alliance should throw into question the wisdom of assuming inordinate economic and military burdens to subsidize the protection of European welfare states.