Bush invaded a sovereign nation that was no threat to the US and cost us more lives than was lost on 9/11.
If there had been no invasion of Iraq there never would have been an ISIS to deal with, so ISIS is the direct responsibility of Bush II as well.
There is no way to clearly say that
"If there had been no invasion of Iraq there never would have been an ISIS to deal with" I'd say that is POSSIBLY true, but on the other hand, the 1400 year history of jihad, killing 270 million people around the world, makes that argument shaky at best. It might be of a higher possibility if it wasn't jihad.
As long as were talking about a US president's responsibility for ISIS, I'd have to say none bears that guilt more than Obama for his 2011 US troop pullout from Iraq, combined with his refusal to clamp down on ISIS friendly banks, and his collusion with al Baghdadi which allowed ISIS convoys to travel
unmolested on open, desert roads in Syria and Iraq (sitting ducks for airstrikes), with only "pinprick" token resistance from Obama.
In contrast, in Kosovo, Clinton hit Serbs with 700 airstrikes a day.