Bush HAD that agreement already. Those ISLAMISTS and JIHADISTS over there in that Iraqi Shia government were just itching for their chance to prosecute those US Soldiers, something Bush wouldn’t let them do.
If Obama had let them prosecute our US Soldiers, I would have been all over his case on that issue.
The Iraqi government was not one of Islamists and jihadis (but it soon will be). This issue could have been finessed. A compromise that met the Maliki government's domestic public relations needs could have been found. The Iraqi's knew they were going to be at the mercy of Iran if we left and they wanted us to stay. It is doubtful that any US soldier would ever have been prosecuted for anything - especially since we hardly ever let any of them take leave off base. Hillary ignorantly chose to make this an all or nothing proposition however, and that is what killed the deal.
As for the Bush administration, they punted the issue to their successors. Understandable since giving ground on the immunity issue would have had a political price. Wanna blame it all on Bush?