An invasion and occupation of Serbia would inevitably draw hundreds of thousands of American soldiers into a combat situation that would last for years. Such a venture could not possibly be sustained on the basis of a volunteer army. It would require the reinstitution of the military draft. All-out war would, moreover, have vast economic and social ramifications, to the detriment of the working population. There would be a vast increase in military expenditures, at the expense of what remains of social programs such as Medicare and Social Security.
Every war generates inflation, which in turn pushes up interest rates.
This would quickly undermine the stock market boom, which has been sustained by an environment of low interest rates and cheap credit. Deep recession and mass unemployment would follow. Anyone inclined to take for good coin the assurances of Clinton that the escalating military campaign in the Balkans will be relatively painless for the US population should recall other major ground wars of the past half-century. The United States stumbled into a war with China after General Douglas MacArthur had assured Truman in 1950 there was no prospect that Chinese troops would intervene in Korea. Vietnam began with the introduction of 16,000 US advisers, but there too, miscalculations, blunders and a vast overestimation of the efficacy of sheer military power to achieve America's aims became the starting point for a bloody conflagration.