The tactical issue is ISIS or ISIL in the greater Levant area, which is essentially Syria, and Iraq, Lebanon, Jordan, et cetera. But the wider problem is not just trans-regional in that part of the world, but it's also global. I mean, 40 to 50 countries supplying fighters to this current fight in the Middle East? Come on.
Given its Internet sophistication and the attraction the group has with vast numbers of potential recruits from among disaffected populations around the globe, ISIS has the realistic potential to eventually swell its ranks of jihadists waging a 'holy war' to hundreds of thousands in both the western and eastern hemispheres.