The message is that Abadi is done with Maliki’s strategy, adopted under intense U.S. pressure, of incorporating Sunni leaders into the central Iraqi government. This change may anger the U.S., since it’s hard to see how else to placate Sunnis and keep them committed to holding the country together. But it makes sense if Iraq is acknowledged as divided already by the presence of Islamic State in the Sunni-majority areas of the country.

In the past, an Iraqi prime minister might have worried about how the U.S. would feel about a Shiite-dominated rump Iraq, which would be something close to an adjunct of Iran. Abadi must be calculating that, having made its own deal with Iran, the U.S. can live with this result as the least-bad outcome — because it’s less threatened by Iran after the nuclear deal.

The U.S. would like to defeat Islamic State, and we assume Iran would, too. The big change, however, is that the U.S. may no longer be as committed to a multi-denominational, unified Iraq as a buffer against Iran. That’s the result of a regional change – brought about by the nuclear deal between the U.S. and Iran.