It is well-nigh impossible to get a US citizen extradited to another country for trial.
Your evidence for this is?
Maybe that will change, in the light of recent events.
What events would those be?
I think (in answer to the question) that those sanctioning, commissioning, or committing torture should be tried. But that's a lot of people.
I agree, both that that would be appropriate, and that it would be a lot of people. However, i doubt that it would be easily done. Recently, i have heard an interview of the Brigadier who lost her job and was demoted to Colonel for the hijinks at Abu Graib, and an interview with the author of the "interrogation" policies used by the Bush administration. The Colonel was very bitter, and expatiated at length on just how many higher ranking officers knew about what was going on, in many cases when she didn't know herself, and how intelligence operatives, who were often not identified by name or agency, would show up at the prison in her absence to interrogate prisoners and to instruct her personnel in how they should and could get away with acting. Her contention was that many, many higher ranking officers up to and including the commander of Southern Command and his staff, as well as members of the administration, were aware of what was going on, but always maintained a position of "plausible deniability" and committing nothing to writing.
The policy wonk as an even more entertaining piece of work. It was almost impossible to get a verb out of him, though the interviewer was an aggressive and veteran journalist. He constantly said in so many words that documents which apparently condone torture were in fact nothing but thought exercises, and were often released as examples of what would not be tolerated, but that those who wished to slander the administration had released them without covering memoranda which explained this. When challenged about why said covering memoranda had not been produced by defenders of the administration, he attempted to change the subject, and failing that, went on the attack, accusing the interviewer of being a member of the conspiracy operating to defame Bush and the members of the administration, and then terminated the interview with a few choice contemptuous remarks.
I suspect that all or nearly all of the responsible parties have their backsides well covered. When i was in the Army more than 30 years ago, questioning the actions of officers would get you in a hell of a lot of trouble right quick, and questioning the actions of non-commissioned offers would get you a shrug or a wink, and "CYA." CYA means cover your ass--and every career soldier, sailor, airman or Marine does that with a competence they don't necessarily show in the performance of their duties.