Original: Post-1965 Post 1965 Immigration was mostly Muslim, and unlike their Chrisitian counterparts they faced a somewhat greater difficulty in assmiliating because of their Islamic faith and the "back to the roots"/anti-assimilationist trend that gripped America in the 1960s and 1970s.
Simplified: After 1965 After 1965 Immigration was mostly Muslim, and unlike their Christian counterparts they found it a bit harder assimilating because of their Islamic faith and the anti-assimilationist trend in America of the 1960s and 1970s.