This question has been answered before by /u/JDolan283, here.

It's worth asking if he did actually "cause" the war. In one interpretation (a source that comes to mind is Misha Glenny's Balkans: Nationalism, War and the Great Powers, 1804-1999), Austria was itching for a fight because Serbia and the Balkans were effectively the only avenue open to it for imperial expansion. It's been suggested that this was a convenient excuse for them to kick off the war and invade Serbia and that, if not for Princip, another excuse would have been found soon enough anyway. Other contemporary commentators had felt that the European balance of power was teetering as well. In this reading, it's not the enormity of Princip's crime that causes the war but the fact that so many parties were ready for it and looking for an excuse. I'm certainly persuaded by the argument that it's hard to give the one guy too much credit/blame when so many other factors were at play.

Perhaps another user in this sub could say how widespread support is for this interpretation.