I find some of the more interesting additions (like all of Argentine Patagonia being Welsh) to be acceptable as it is your mod, But I would like to share a few states I think might have been possible mistakes.

Firstly, Cumbria in northern England is listed as English, when all of it's surrounding states are the culture you assigned to Northumbria.

Secondly, The state of B.E.T. in present day Chad is Cyrenican culture, when Berber surrounds it on two sides and I assume would be more appropriate.

Lastly, I personally think that Russian and Han Chinese are represented A lot more homogeneously that most of the other major's main cultures. I think at the current scale something like Siberian for Russia, or one of the southern dialects in China like Wu should be represented to keep the same scale.

If any of this was intentional, I am fine with that.