These are all great examples of ways to alter the campaign setting.

To be clear, I don't think anyone is advocating or encouraging DMs to make changes just for the sake of making changes. Rather, there are, I believe, any number of ways to make alterations for the purpose of making your particular Birthright campaign better. If it ain't broke, don't fix it (as they say).

These cultural changes are a great example of putting this theory into practice. The value in altering how we, as DMs, present a particular culture to our players is an increase in accessibility. Many DMs find it difficult (or off-putting, even) to try to present a culture in the setting that is modeled after a real-world culture they are unfamiliar with.

Also, Birthright was created to facilitate domain play. Conflict between religions, cultures, and kingdoms is baked into the setting. But what if you are running an adventure-based campaign and social conflict isn't one of the themes you're looking to explore? Making Cerilia more global in nature with certain basic facts being commonly accepted across the continent certainly makes a DMs life easier. Racism is something many of us don't want to have to deal with in the real world -- why would we want to have to deal with it as part of a game we play for entertainment? Animosity between Sidhe and humans can be a fun part of Domain level game play but if that's not what your campaign is about, it may serve you better to have a general acceptance of peoples differences and keep the bigotry and racism as elements of antagonists and other characters who are presented specifically as being evil.

[Sorry, I didn't mean to interrupt the conversation. Please continue! I just wanted to take a moment to connect some of the dots for people who may be here looking for inspiration and practical advice. And if there are other ways your campaign benefited from the examples you are sharing, please feel free to highlight them!]