What is the Catholic position on ethnic parishes today? I was thinking about this comment concerning cliquishness in the churches and how they can help build each other up (or avoid strife).

Smaller towns in rural America with large immigrant Hispanic populations often have Mass in Spanish usually with a visiting pastor. It once was the case that there would be a Polish church and a German church and an Italian church and maybe an Irish church in different neighborhoods.  But nowadays, we're lucky if there's one church for a 30 mile radius and we have to share resources.

I just wonder what the official status of these sub-parishes is.  If Mass is only offered in your native language once every month is that all you're obligated to attend?  Is Bishops goal of having Hispanic outreach to just get people in the door or to make them full fledged parishioners?
My church (Roman Catholic, on the south coast of the UK) hosts a monthly Mass in Polish, which is well attended. The building was packed for the Polish "Midnight" Mass at Christmas.

It also hosts a weekly (Sunday afternoon) Mass for the Ordinariate congregation, whose members are not members of the local diocese.

In all these efforts, including the Hispanic Masses you reference, I would like to think that the Church is not just seeking to get people in the door, but providing a ministry. It is to be hoped that immigrant churchgoers will seek to assimilate themselves into the local culture, and there is at least a weekly opportunity to attend Mass in English, which would fulfil an obligation. But such assimilation may take some considerable time. If the Church can provide the opportunity for confession and Mass in a native language, and allow full participation in the rites of Church, then why not?

[The answer to Why not is, of course, your point about making fully-fledged parishioners. However in our case, it's quite likely that members of the Polish community are not long-term residents. We do have a sizable Italian Catholic community, and they do attend Masses in English.]