I see a lot of my own thoughts in your post. Art history student here.
I read of the destruction in cities like Lyon, Saint-Denis, Noyon, and Toulouse, and my heart hurts a little. Just to have seen the works of the faith that built those churches and cathedrals and to know that the bond that ultimately allowed Europe to be is now meaningless to such a large percentage of the population. And how could Europe not but come unwound? The church, all but abandoned after having arguably given life to the possibility of nation states, is now left lifeless, and without it, I don't see Europe rising again as a collective entity.
Really, is there any source of unity in these nations outside of anti-Americanism? As you said, there is little nationalism left outside of the hollow cheers for a soccer team. Precious little to bring the French together outside of negatives (anti-American sentiment, racism, etc...)
It does sadden me. I do feel a bond with Europe, having traced my ancestry well back into medieval England, but I honestly can't hold on to my past when the heirs to that past reject me and reject that past.
So I sit the fence, hopeful that France turns around and doubting it ever can.
Having spent time in Spain I can tell you that the country is covered with castles and mosques from the days when Islam ruled Europe. It was Ferdinand and Isabella that finally expelled them. Now they are back but Europe has learned nothing from their own history, and will probably fall again.