Quite apart from the fact you first sentance makes no sense, you're otherwise wrong.
Had we not been bone headedly intervening in places like Iraq, there would be no ISIS today. We can extrapolate with a fair degree of certainty on that (even Clive conceded that point). There were a few Islamic groups in Iraq in the 1980's but Saddam Hussein had pretty well destroyed them. The only active group was operating under the protection of John Major's no fly zones, much to Saddam's annoyance as he wanted to kill them too.
Similarly, Gadaffi was in the process of pushing back the rebellion in Libya which would have been defeated within a week, before we intervened there and opened up the vacuum that AQ in the islamic magreb are now exploiting
Boko Haram you can argue about. They've been knocking about for a tad over a decade but its only in the last couple of years when they've adopted ISIS that they've become a threat. Would this have happened had ISIS not been around to provide the stimuli? I don't know. Their strength owes a lot to the fact that the Nigerian government are ambivalent to them given that they're murdering people who don't vote for Goodluck Johnathon, but they'd actually been one of the easier groups to defeat
I'd be pretty confident that what we would now be facing instead is a disparate group of terrorist organisations, which to a large extent is what Islamism always was prior to 1990. Your first line of defence would be the armies and secret police forces of the hosting states, and although they'd be pinned down dealing with this domestic threat, the evidence suggests that they were on top of it for the most part
The only places where such activity could gain traction would be failed lawless states like Afghanistan, Yemen, and Somalia. You wouldn't be seeing the likes of Syria, Iraq, and Libya drifting violently into fundamentalism
The other unknowns of course are what effect not having a quarter of million military personnel pinned down in Iraq for a decade might have created for us by way of opportunity cost. Also the fact that when civil wars breakout we get populations displaced and some of these (not as many as popular myth would have us believe) end up in Europe. Of these, some will radicalise unable to adapt and become domestic threats
There's a lot of people seemingly who made catastrophically gung ho noises back in 2003 who can now see that their judgement has been spectacularly wrong and seek instead to qualify things by blaming an aspect of the planning (something that didn't do at the time). I also think it's natural enough that they seek solace in an imaginary comfort blanket that all of this would have happened anyway (as you're doing). Put bluntly, there isn't a shred of evidence to support the view that it would have happened on anything like this scale. The most likely scenario you would have had is a series of terrorist groups linked together by a concept of quasi nationalism in the case Aleppo, and an emerging radical Islamist charcater. Nothing new in other words. You wouldn't have sovereign states (even we don't recognise them) running about with abandoned American made weapons that the Iraq army threw down. Indeed, the Iraqi army as was, would have the very same people who make up ISIS today fighting in defence of Ba'athtists and Saddam
If you want an example of how a small incident snowballs into warfare then look no further than the driver of Franz Ferdinands car who decided to take a different route back from the Trade Hall. So yes, this seemingly innocuous action that drove him past a patisserie in which Prinzek happened to be sitting with his weapon still active set in train a chain of events that ended with the deaths of millions, the birth of communism, and sowed the seed for the emergence of nazism.
Historical causation is a multi faceted creature but your notion that the invasion of Iraq is something of a footnote can't be stated so unequivocally.
