We know that there are many UPGs coming to America as diaspora groups–Saudi, Thai, Vietnamese, and Iraqi just to name four obvious groups. There’s a lot of complexities involved in identifying the groups that are here, and even more in identifying which ones are unreached (because a lot of Christians from unreached countries come to America for one reason or another) and developing strategies to reach them.
Today I learned about an effort to map the groups within the 100 largest metropolitan areas of the United States. Some 65% of America’s population live in these 100 MSAs, and if you map the peoples within those areas, you will have mapped all of the UPGs in the USA (there’s quite a lot of intellectual work in this) with the one exception of the Native American groups (which are a special case, and for which a different approach to mapping them is being taken).
Note that I’m not saying you will have mapped all the unreached individuals. Rather, the idea is that you won’t find a new, unique UPG in a city outside those 100 MSAs (at least theoretically).
The effort is being championed by the IMB and several of my friends there. You can read more about it and get involved at http://www.usapeoplegroups.org.