One way of looking at The Monroe Doctrine was that it involved unilaterally declaring the New World (aside from Canada and a few other bits) was a protectorate of the United States. And that is a kind of imperialism - after all, much of the British Empire consisted of "protectorates". And "protection" is a well established modus operandi for other organisations too such as teh Mafia. I wouldn't be surprised if the Al Qaeda brand gets used for that as well...