The United States, like Germany, came late to the empire business. It did not aspire to informal Empire, but rather went to great lengths to undermine the existing empires to open them up for US business. Eric Louw tells the story very well:
Louw, P. Eric. 2010. Roots of the Pax Americana: Decolonization, Development, Democratization and Trade (Manchester: Manchester University Press).
In his account, the US was going to great lengths to undermine Britain's Empire, especially India, even when those powers were allies during the Second World War. He attributes Chamberlain's behavior in Munich to a justifiable fear that dependence on US support in fighting the Nazis posed a greater threat to the empire than the Nazis themselves. He shows that the US made good use of Gandhi in discrediting the British Empire.
Rather than going to the expense and trouble of maintaining a formal Empire, the US preferred finding compliant regimes in important venues. For example, the US could have kept Cuba as a colony, but it got what it needed much more cheaply by keeping friendly governments in place. In contrast, Puerto Rico, which was much smaller, would not pose much trouble as a territory controlled by the US.
The book does not seem to be intended as a radical critique. It does not discuss how this Pax (Pox) Americana proved to be a disaster, leaving people under the rule of Marcos, Mubarak, the Shah, and other such klepocrats and thugs I am anxiously waiting new chapter being written today in the streets of the Middle East.