As someone who is scheduled to study imperialism in London this fall, this quote struck me as particularly interesting. The powers of the executive have been expanding way back to Lincoln and Jackson, but imperial presidency implies dominion over other nations.
America can rain hellfire from the sky upon any location in the world if it so pleased. This isn't simply dropping nukes and ending all life, but specifically killing individuals. We own the seas. Indeed, the Navy's slogan is A GLOBAL FORCE FOR GOOD but it should probably read A GLOBAL FORCE FOR NOW.
Obama's presidency, internationally, is imperial. We occupy foreign countries and maintain military bases in countless more. But this whole debate is whether we the hegemon, the metropole, the imperial center are to be ruled as the perpipheries are. Can drones that kill Pakistani families every other day be used to slay gun-toting self-proclaimed anarchists living in the forests of NorCal? I hope not.