This idea does not really exist in France. We don't use to classify people according to their religions, sexuality or tastes (although this trend is slowly appearing) which we think must remain in the private circle. Communautarisme means that people classify themselves according to some private attributes instead of feeling that they belong to a whole.
For instance: I am French, born in Provence and I am protestant.
Nevertheless, I place my belonging to France as my first attribute. I define myself as French first, not as a protestant woman.
Therefore, I see other French people not as catholics, jews or muslims, but as French. If I would apply the notion of communautarism, I would feel inclined to not feel I am belonging to the same group as those people, what would lead to some form of denial of our common roots.
My suggestion:
community withdrawal
Multiculturalim ne convient pas, car il s'agit de la forme positive (et souhaitable !

) de l'acceptation de toutes les différences, alors que le
communautarisme est une forme extrême et négative dont les conséquences ne vont pas vers la compréhension mutuelle, mais le repli.