“The game has changed. Enough is enough. The border needs to be sealed,” a senior Obama administration official said of Washington’s message to Ankara. “This is an international threat, and it’s all coming out of Syria and it’s coming through Turkish territory.” ... “This is really a question of their border security,” a senior U.S. official said of Turkish authorities. “They need to step up their game when it comes to this and they can’t necessarily look to us to fortify their border for them. Paris is a wake-up call to them that this is a problem they don’t have under control.” ... Before Paris, Turkish officials often rebuffed U.S. calls for a larger border force, saying the frontier was simply too long to effectively seal, no matter how many soldiers were deployed. Turkish officials pointed to Washington’s inability to seal off the U.S.-Mexico border as an example of how difficult such operations can be. U.S. officials chafe at the comparison. “If we were at war with Mexico, we’d close that border,” a senior administration official said of Washington’s response.