My only comment is the use of "Northern America" vs "North America."
I had made that change at one point, and then changed it back. They explain it on the website: North America is Northern America, Central America, and the Caribbean. One of the reasons I like their system is the subgroupings. I could have included a higher "North America" tier, but I was trying to minimize extra layers.
Interestingly, they don't include North America either, even though they do have a classification for North America - actually, they group Central American, the Caribbean, and South America under "Latin America & the Caribbean", which makes sense from a perspective of cultural & linguistic groupings.