It’s not “segregation”, why would you think that? I’m frankly appalled that you would make such a remark.
There are parishes that are “nationality parishes” where, among other things, people from certain countries or areas can hear regular Masses in their native language (not English), celebrate the feast days that they celebrate back in Poland or Mexico or wherever (not necessarily celebrated or made such a big deal out of at their regular parish church), and have other customs they’re used to having “at home”. In some cases these parishes preserve a historic church that was in the middle of some neighborhood that used to be Little Poland or Little Italy but the original residents moved out to the suburbs and now their grandchildren live somewhere else, but need to preserve their heritage. Everybody is still welcome to come to the Masses at these churches, you don’t get thrown out if you aren’t the correct nationality, but it’s kind of like going to church in Italy, or Poland, or Mexico, etc.
The Latino parish in my area in Pennsylvania was something the Latino community wanted because many of them do not speak English or have cars and the closest parishes that had Spanish-speaking Masses were a ways away. There were some priests and nuns running around trying to minister to them and it was very difficult for them. The Diocese also for some weird reason did not want them to have their own church/ parish for years even though the same Diocese has multiple “nationality” parishes for Polish, irish, Italian etc. I have no idea what the problem was. Maybe they thought it would look segregated. Finally a wealthy Italian man felt called to donate to the Latino community all the money for a new church with plenty of space right out in the area where they work, and they were very happy and built the church and named it after the man’s patron saint and did in the end get Diocesan approval for it. I’ve been out to the church for the Our Lady of Guadalupe feast and they have the dancers and the traditional service and about six Masses that day all of which are full (the one I was at was standing room only and they had about 6 guys parking cars).
The town I live in, which is about 20 miles away, also has Spanish language mass once a week, as do several of the other surrounding towns, and we have Latino people attending those and also the English language services with us, but I’m sure some of them go over to the “nationality” church once in a while as well to feel a bit more at home. Nothing wrong with it.
Edited to add, here is also explanation from Wiki