Good question, and to my mind the answer is... kinda! I can totally see why you'd come to that conclusion because we live in a post nation-state world and most of us live in clearly defined states and so we tend to draw on our life experiences to examine the world around us. But the modern idea of a Caliphate has a lot of intellectual history to draw from across a very long period of time, most of which predates the modern idea of a nation-state.

I apologize for how freaking long this is and I wouldn't blame you for not reading it. I use Reddit as a way to sort my thoughts out on a topic sometimes, in the hope that people will explain where I've totally dropped the ball and I learn something.

The idea of a Caliphate in part hearkens back to the OG caliphate, the one founded by the descendants of Muhammad himself, since a Caliph is meant to be the official heir to the Islamic world Muhammad left behind, and the one successive Muslim governments have tried to emulate, like in Spain, Egypt, etc.
It's not the same as the sort of nationalism where the cultural and historical ties to the land you live on, and your shared history, language and culture are held up and revered in order to promote social cohesion and loyalty to the state (a very trite, very reductionist definition by me). The unifying factor here is religion, not state of origin, and the Umayyad caliphate, for example, didn't give two shits who they ruled as long as they were peaceful, payed taxes, and were Muslim unless they were happy with paying more taxes, in which case they didn't care about the Muslim thing either. This is very similar to the way most things were run back then - Romans didn't care if you weren't born in Italy if you paid taxes and kept your head down, the Normans didn't care that their subjects in England didn't even speak French as long as they worked the land, etc.

But, that's not the only history ISIS is drawing on. Obviously they see themselves as the rightful successors of Muhammad and so worthy of running a caliphate, but Islam has a relatively recent history of political organization in response to the rise of nation-states and colonialism especially that I'd bet my bottom dollar has an impact on whatever intelligentsia ISIS has hovering around at the top, sending people off to die to benefit themselves and their buddies.

People like Jamal al-Din al-Afghani, who spent the 19th and 20th century trying to create a real, proper nation of Islam, a coherent whole that could oppose the West at not just a raw, physical level, but at its most basic intellectual level - reexamining Islam to try and make it viable in a rapidly changing world where Social Darwinism was the ruling ideology. al-Afghani himself traveled the world, Islamic or not, trying to create Islam's first massive political reorganization, not just a reorganization of an empire or kingdom that happened to be Islamic, but a reorganizing of the way Islamic people organized themselves politically now and in the future. Islamic Modernism, Pan-Islamism, ideological frameworks for future Islamic peoples to organize and respond to Western pressure. This kind of thing never went away. Colonial incursions into Islamic regions was, in polite terms, a tire fire; it started burning then, it's still burning now.

So yes, there's an element of nationalism as the West understands it, implicit in ISIS. But the ideological background they're drawing from is not Western, and shouldn't be described in Western terms - ISIS is not unique in this either, the 9/11 bombers, al-Qaeda, the Taliban, the Iranian revolution, all have their roots in responses to real or perceived Western aggression and a desire to ferment a pan-Islamic response to it and reexamining what Islam was, is, and should be. When things seem as truly, fundamentally broken as they must do for many in the Middle East, and for the poor and marginalized in Muslim nations around the world, that idea of change has combined with the perception that violence is the only way to make their voices heard, and seize a place for themselves in the world.

I want to be very clear here: obviously that does not come close to justifying any atrocity, ISIS should be wiped out, the Taliban ran one of the most brutally evil states in recent memory and al-Qaeda and the 9/11 attackers are all murderers and if I believed in Hell I'd want to see them burn in it. Their 'reexamination' of Islam was basically a means of justifying an ideological purge and power grab and whilst it's important to understand the ideological backgrounds of these things, like all ideologies at one time or another, its been used to justify murdering anyone who doesn't fit the mold of the world they're trying to build. Fuck them. But that doesn't mean they're not coming from somewhere worth understanding. I'm firmly in Robert Fisk's camp here: a lot of the insane violence you see in the Middle East and elsewhere is precipitated by very legitimate grievances, regardless of whether or not the responses are acceptable. We do ourselves a disservice if we don't try to understand a history of Islam and try and understand where organizations like ISIS come from. If we pretend like they're just crazy evil monsters who came about because they're evil and do evil things because they're evil, then this is never going to end, ever.