The issue here is based on two things. First, Tableau includes cities with the size of 10,000 or more. Carlsbad, TX, for example has a population somewhere in the neighborhood of 1,500, so we don't have it in the product currently. The second issue is that in the Edit Locations feature, unrecognized cities are grouped by their name. So all instances of Carlsbad that are not recognized will get mapped to one state.
Right now, the best way to work-around this limitation is to geocode the cities outside of Tableau and then use that Lat/Long information on the map instead of the generated Lat and Long values. You can also use the custom geocoding feature in a similar way.
We are aware of this limitation. It's something we are looking to address in the future.