Without the Iraq war stupidity, ISIS would not have the influence and power they have today. It was a direct result.
I'd say the bigger problem wasn't the war itself, but the way the U.S. handled the aftermath... The way they disbanded the military, etc. But I also think there were other players: The Syrian government (who took no efforts to deal with ISIS early on, and in some cases supported them), the whole "Arab Spring" (which also had a destabilizing effect.)
But regardless of the cause, the end result is the same... a large group of individuals (citizens in Iraq/Syria living in/near ISIS territory) who are subject to significant repression. Having Canada sit back and point fingers doesn't help those people. And while the long term solutions will be more complex than "Lets bomb them", in the short term military action is probably the best way to go.