This will result in a drop in US troop casualties as the reduction in combat forces in Iraq resulted in the same, which removes all mainstream criticism in the US of an American war. As long as American soldiers aren't dying in the dozens each month there is no real domestic opposition.
I don't find insurgency against a conventional military entirely productive (attacking the formulators and beneficiaries of a policy is easier, less costly, and more rewarding) but it would likely result in total US military disengagement if Jihadists were to kill thirty or so servicemen in a single attack... a moment such as in Beirut or Mogadishu.
What is the nature of these troops? Do they include mercenaries and CIA operatives? The withdrawal of 33,000 supply line grunts, mess hall workers, nation builders, and lesbian recreation bureaucrats would not constitute troop withdrawal.