Under NATO, U.S. forces might help suppress the Islamists in Europe, but the U.S. Forces have been weakened and the upper power structure infiltrated by Obama appointees..
There is still Australia and Canada. They could come to Europe’s aid, if Nationalist leaders arose. Similarly, Russia under Putin is supposedly funding nationalist leaders in European countries...
France reportedly has 30 million guns, most of them illegal.
Germany is not completely disarmed. Switzerland is an army.
Norway and Finland have significant arms.
An alternate scenario is for the Muslims to simply out breed the Europeans. They are looking to do this in only two generations.
Good points, and thanks.