I was working on the assumption that there will be no sudden withdrawal.
Not based on any special knowledge, simply on the basis that a sudden withdrawal in an election year doesnt seem likely to me. Even if the WH were to decide they want to, as you say, "bug out", it will be one long slow bug out.
I think withdrawal will eventually make things much harder for GHQ, not easier, but nobody said things will work out smoothly. I am just saying 200 million people, a 150 billion dollar economy, a large army, its going to drag on for years and years yet. And maybe even get better at some point.
I am also assuming that with a nuclear power, with china, with "needs" re Iran (which, frankly, I cannot comprehend), the US will find it in their heart to step back and try again, and again, and again.... Not happy, but willing to grit their teeth and give it one more chance "for the sake of the kids".. there can be mutually assured corruption from many angles.
I could be wrong, but I try to be optimistic.