You're using a filled map/choropleth, which means that some geographic area is filled. So, how would you want to show "ALL"? You'd need some sort of geographic boundaries, but that doesn't make sense for the whole world.
If you were using a bubble map, then you could pick some arbitrary spot on the map, say in the middle of the Atlantic or Pacific, find the latitude and longitude, then enter that latitude and longitude into the Edit Locations screen.
I suspect, however, that All does not truly mean every single county in the country, correct? If it did, then your best bet may be to do some additional data prep to break each of those records for "All" into individual records for each county.