doesn't that mean that it's a good thing when immigrants keep their culture alive?

I live in a small town (approx 3,600 people) in the middle of the USA in a culturally rather homogenous state. My town however is about 50% Hispanic. There being such a concentration of Hispanics has made it possible for them to maintain many traditional ways. There are four Mexican restaurants, three grocery stores (small ones) and a bakery. There is a traditional dance troupe that marches in the annual fair parade. There are, of course, many smaller more personal ways in which their culture is kept alive. Our school district has a bilingual program (optional, not required) so both of my sons are taught the normal curriculum in Spanish for part of the day. I think my town is much the richer for all this.

In Cedar Rapids, a city about 45 minutes from where I live, there are a large number of people of Czech descent (the National Czech and Slovak Museum is located there). Years ago they were ridiculed and discriminated against. They were not allowed to speak their native tongue in public. Many living traditions were lost. There has lately been a move to revive many of these traditions. There is no intention to remove themselves from mainstream American culture (such as it is) but rather to reclaim something of their heritage. The Hispanics in my town won't have to reclaim anything because they will not have given it up in the first place. I say again that my town is much the richer for this.