chapotraphouse

Usually there are a couple of churches in a diocese that do it once a week with the express permission of the diocese. There have been instances of diocese forbidding priests from doing it, or from performing the Eucharist during it (with the general ideological split being if the diocese sees these masses as an outlet for wacky conservative Catholic frustration, or as a gathering place for wacky conservative Catholics to create a different, heretical sect), but in general most of the large population centers in the U.S. will have at least one church that does one mass in Latin a week, usually on a weekday. Monasteries also generally follow their own dictata and are often done solely in Latin, with them only holding common mass in vernacular.

Orthodox Churches are even weirder about this, with them only holding mass in the vernacular that the Church came from (so a Serbian Orthodox mass in Los Angeles will be done in Serbian).