Great empires, such as the Roman and British, were extractive. The empires succeeded, because the value of the resources and wealth extracted from conquered lands exceeded the value of conquest and governance. The reason Rome did not extend its empire east into Germany was not the military prowess of Germanic tribes but Rome's calculation that the cost of conquest exceeded the value of extractable resources.
The Roman empire failed, because Romans exhausted manpower and resources in civil wars fighting amongst themselves for power. The British empire failed, because the British exhausted themselves fighting Germany in two world wars.
In his book, The Rule of Empires (2010), Timothy H. Parsons replaces the myth of the civilizing empire with the truth of the extractive empire. He describes the successes of the Romans, the Umayyad Caliphate, the Spanish in Peru, Napoleon in Italy, and the British in India and Kenya in extracting resources. To lower the cost of governing Kenya, the British instigated tribal consciousness and invented tribal customs that worked to British advantage.
Parsons does not examine the American empire, but in his introduction to the book he wonders whether America's empire is really an empire as the Americans don't seem to get any extractive benefits from it. After eight years of war and attempted occupation of Iraq, all Washington has for its efforts is several trillion dollars of additional debt and no Iraqi oil. After ten years of trillion dollar struggle against the Taliban in Afghanistan, Washington has nothing to show for it except possibly some part of the drug trade that can be used to fund covert CIA operations.
America's wars are very expensive. Bush and Obama have doubled the national debt, and the American people have no benefits from it. No riches, no bread and circuses flow to Americans from Washington's wars. So what is it all about? More