I think every one here wants this mess wrapped up. I've got a son in the Armed Forces and as a veteran, I do support the superb job the military is doing in a rotten situation (my opinion) but it's very hard to compartmentalize and support the troops without getting angry about how they got dumped into this mess.
Good that you are supporting your boy; nothing finer in my opinion than to support family in any circumstance. :thumbup
If you do not agree, the I suggest writing to those who agree with your situation, and get a large enough list that encompasses a large region of people, and petition the next president to get out. I would not bother writing your Congressional representative; although they may attempt to set dates for troop withdrawal, but that is not their function:
Congress should have nothing to do with a war, except declaration and appropriation of funds. The commander in chief is the top military official, and therefore controls the war effort. As such, the chief needs to be known specifically, by a large group of peoples across the nation, that his/her war-time actions are not vindictive of the populace, and should reconsider his/her choices in the war.
I suggest to keep it as a business-type complaint-format. I am not sure if a specific action suggested by you and your fellow petitioners would be the best, because you may or may not have all the information he/she has as the top military official.
I would encourage all of you who do not support the war to write to the next president, indicating your lack of support for the war; if the letter count is significant enough, the president may decide the effort is not worthwhile enough to continue, and bring the troops home.
Of course, as you say, we made the mess, we should clean it up; however, war cleanups are even messier.