IS was created after the US destroyed Iraq, based on false evidence (just like America invaded Afghanistan based on false reasons). The damage is done, but why

IS was created after the US destroyed Iraq, based on false evidence (just like America invaded Afghanistan based on false reasons). The damage is done, but why persist? What do you expect to happen exactly? In fact Russia consolidated its influence and alliances in the middle east just by exploiting American mistakes there. Just leave. It would be a hugely popular move everywhere: among the left, the right, veterans, other countries, etc. So why not do it?