Eventually the question will be asked -- "Who lost Iraq?" In a way, it might be seen as an improper question to ask since it presumes that Iraq was ours to lose. The fact that it was not, however, doesn't absolve us of responsibility.
Immunity for U.S. troops post-2014 isn't going to happen. It's a political non-starter. No Afghan presidential candidate, queuing for the April 2014 elections, can support it, nor do the Afghan people want immunity for foreign troops.