There are a few facts about this map that sum up it's usefulness:
1)There was no attempt to normalize the data. For example, the study used for the USA is a study that measured NBPEL. The NBEL size in that study(Wessells) was a little over 5 inches - I think around 5.1 inches. The Germany study was BPEL, and the average was around 5.7 inches. By just looking at the map, you would think that the Germans are significantly bigger than the Americans. But they're not comparing apples to apples.
In the US study, they also measured the fat pads, and the average was a little over 1 inch. I'm approximating here, but it was something around 1.1 inches, if I remember correctly. I never read the study, so I don't know whether they measured the fat pads when the guys were flaccid or erect. For me, it makes a big difference. My fat pad always seems closer to 1 inch when flaccid and .5 inches when erect. So I don't know if you can just add the fat pad average to the NBPEL average to get BPEL, but regardless, the BPEL number for the Wessells study is definitely more than 5.1 inches. It's probably in the range of 5.6 - 6.2 inches. This means the guys in that American study were either right around the same size as the Germans, or maybe slightly larger.
2)Even beyond BPEL vs NBPEL, there is no mention of the rest of the methodology of the studies. Some of the studies were online surveys, I believe. There's no mention of whether the subjects were picked randomly or if there was self-selection. I've also come across several studies(outside of this map) that involved men with ED. I'm sure there are some of those on the map.
3) I couldn't find medical papers for any of the South American or African studies. If anyone has, please let me know. I would be interested in seeing them. I'm not doubting that the averages could be different in different countries, by the way. I think it's very possible. I just don't think this map has the answer.
If anyone can post a link to any of the studies on the map, please post. It would be be interesting to see how many of these are legitimate studies.