Apparently, Americans do like the retribution aspect of it:
http://voiceofrussia.com/2014_05_04/Americans-like-death-penalty-because-they-want-prisoners-to-suffer-US-sociologist-5620/
If it is to be carried out, the Taiwan method would doubtless be the most effective.
Execution by shooting is the most common method of execution in the world, used in over 70 countries. Whilst most of these countries use the firing squad, single person shooting is still found. In Soviet Russia, a single bullet to the back of the head was the most frequently used method of execution for military and non-military alike. This is still the main method of execution in Communist China though the gunshot can be to either the neck or head. In the past, the Chinese government would ask the family of the executed person to pay the price of the bullet. In Taiwan, the prisoner is first injected with a strong anesthetic to render him senseless and then a bullet is fired in to his heart.
I'm sure it would be easy to rig a pistol/rifle so that it's fired remotely. One could have 3 executioners with 3 buttons, with only one rigged to the apparatus.
Simples.