Over time, Iraq’s Sunni minority — notably in western Anbar Province, site of anti-government protests — may feel more commonality with eastern Syria’s Sunni majority. Tribal ties and smuggling span the border. Together, they could form a de facto or formal Sunnistan. Iraq’s south would effectively become Shiitestan, although separation is not likely to be that neat.

The dominant political parties in the two Kurdish regions of Syria and Iraq have longstanding differences, but when the border opened in August, more than 50,000 Syrian Kurds fled to Iraqi Kurdistan, creating new cross-border communities. Massoud Barzani, president of Iraqi Kurdistan, has also announced plans for the first summit meeting of 600 Kurds from some 40 parties in Iraq, Syria, Turkey and Iran this fall.

“We feel that conditions are now appropriate,” said Kamal Kirkuki, the former speaker of Iraq’s Kurdish Parliament, about trying to mobilize disparate Kurds to discuss their future.

Outsiders have long gamed the Middle East: What if the Ottoman Empire hadn’t been divvied up by outsiders after World War I? Or the map reflected geographic realities or identities? Reconfigured maps infuriated Arabs who suspected foreign plots to divide and weaken them all over again.