Are you subject, in your view, to the laws and jurisdiction of the country you're in whilst (a) in combat, and (b) following orders ?
If you were ordered to do something potentially controversial (say, attack a house containing civilians using grenades and other relatively non-targeted weapons, to try to kill an enemy leader inside) would you expect that any potential retribution for your actions would be dealt with through the US military & its disciplinary structure rather than any civilian court ?
PS I'm not trolling, I'm genuinely interested in to what degree you can be confident that, if you're following orders, then you are (excpet in exceptional circumstances) accountable only to the US military structures.