My feet don't look like either English or Irish feet, more of a combination of both - narrow like Irish but toes more like the English? - which makes sense since my ancestry is neither English or Irish.
The point, though, isn't that if your grandmother or grandfather came from Country X, then you are going to have feet that look like Y. What I get from the archaeology journal article is that there is a very wide genetic variation in foot shapes, and as Sumokitty pointed out, the US has more genetic variation, so US manufacturers are going to cater to a wider variety of foot shapes. (As I've said previously, I've noticed that there is a wider variety in clothing sizes available in the US as well, which also probably has to do with the US having a more diverse population.)
For myself, I think my problem may be that while I wore a medium width shoe in the US, I may be a narrow width in the UK. Now I just have to find out where I can find narrow width shoes, as I don't recall ever seeing them anywhere.