What you're talking about depends on many factors, including place or origin, income, education level, etc... The factors are the same for any incoming foreigner - The negative cultural aspect of rejecting assimilation comes from facing too many hurdles and having no real incentive to do overcome them. What you're referring to are those individuals who came from lower-income towns, villages, and cities in a predominantly 3rd world country(countries), meaning the barriers to assimilation are greater than most. Those barriers are not made any easier by mentalities that have been shared in this thread...
I transitioned careers from Social work to Pre-K Education just before the great recession hit and our local Hispanic population began to self-regulate some. In doing so, I was able to be an active part of repairing these issues as much as possible. Back then, we were still getting large annual influxes of new residents, many of whom who had no English background whatsoever. We started a program called the Family Literacy Program which focused on all facets that we could do anything about. Childcare was offered during the day for those children who were not in school. The morning program taught English as a second language to adults (4 hours a day, 5 days a week) and the evening program tutored them in preparation for their GED, while also taking on their school-age children for tutoring, mentoring, instruction, etc. (also 4 hours a day, 5 days a week). It was quite successful until funding ran out, which is a big problem with State run initiatives.
Anyway, moving into the classroom allowed me to take that experience and apply it to 4 year-olds, many of whom had been removed from their homelife for the first time ever and placed into a shool building where only 2 of the 60 staff members spoke a language they could understand. Pre-K classrooms in Georgia are limited to 20 children per class. We had two teachers, myself and an ESOL "expert" who didn't speak Spanish... By the Christmas break, year after year, I could have my non-verbal students not only being verbal, but bilingual, which allowed the second half of the school year to operate much more productively and fluidly. It was all great fun.
I say all of that to reiterate the fact that complaining about a problem is easy. Fixing a problem is hard. And if you aren't helping to create solutions, you're as much of a burden as the problem itself.