Where is this Muslim army coming from? You can't honestly believe an Arab army will form, pass the US and Israeli forces, and invade Europe?
Short term I think Iraq falls under Iranian influence, the Saudis destabilize, and militant groups gain strength across North Africa.
They oppose us as the "Great Satan" and the Christian Crusaders that support Israel. So to them, this means they want to destroy NY and Rome - Israel's strongest allies. Those would be their top targets. Besides Turkey-Greece, the shortest route from the Arab world to Europe is Libya/Tunisia to Italy. Rome has long been a target of radical Islam, though most are not aware (it's historical). They have some whacko prophecy that to conquer Europe they must first take Rome. I think they will try to nuke NY with an inside nuclear device to disorient us and try to keep us backed off. So, we must remain vigilant.