As far as our presence bringing them new recruits, fine, American bombs don't discriminate between new and old terrorist, they just blow them up equally.
The Germans and Japanese held up among civilians too. It didn't help them.
ISIS has free reign until America elects a republican president. Then their days are over. Now it's true that the republican president might mess up the peace afterwards but ISIS will be too dead to gloat.
No enemy likes to meet the American military at full force. Have you ever read the accounts of the Vietnam war by Vietnamese soldiers? They admit they while they managed to make America eventually quit, they got their butts kicked in every battle and they admit they only won because America allowed its politicians to run the war rather than its generals.