@jangsunny1030,
WOW Jang what a challenge
"in" implies groups of one sort or another already exist but that each one suffers internal disjuncture which you'd found difficult to address; confusing
"to" or better yet "into" would better express the idea that each of these groups might already well integrated but that you've found it difficult to reconcile them with the existing sociological structure
"for" suggests an activity separate from the society itself, finding it difficult responding to its need to incorporate subcultures
Very complex; doubtless controversial, splitting hairs indefinitely