I think it's better to leave citizenship out, or focus on treating your own citizens. The rest should follow (this is also what Scahill says in the following story): American citizenship does not protect you from targeted assassination.
No, American citizenship does not great a blanket protection against being killed by the military while waging war against the U.S. It guarantees you nothing more and nothing less than "due process." What process is "due" (literally, "warranted") is an inherently context-sensitive question. What process is "due" to someone who spent a decade waging war against the U.S. while refusing to submit to the justice system of any country?
What justice is due for a 16-year old who grew up in Colorado and has an "unresponsible" father? Are some people classed as waging war by speaking? Are their children classed as combatants from the moment they turn six years old?
The trouble with making it context-sensitive like that is, how do you demonstrate that the person deserves the lower standard?
Your question is mis-phrased. It should be stated as, "What process is due to someone who is accused of spending a decade waging war against the US?"
It appears to be to be completely nonsensical to use the gravity of the accusations against a person to decide what kind of trial (or not) they should receive. The whole point of the trial is to find out whether the accusations are, in fact, true.
Don't ignore the teenager son who was also a victim, separately. No one in government has been willing to admit that this killing was anything other than intentional.