It's not about the geography. It's more about development (e.g. money) and culture -- and in essence an arbitrary historical capture of the term by Western Europeans and WASP-like Americans to mean themselves.
It's best to not thing such terms as about what their etymology or direct meaning is "western = west", etc, but instead consider how they are used in practice.
>I'm not just arguing about the geography, but about the culture. I feel much more like a Canadian or a USian (or a Guatemalan) than I feel like an African, Middle Easter, East Asian, or South Asian. I speak the same languages as Europe, have been mostly exposed to Christianity and its cultural heritage, read the same books and watch many of the same shows as Europe, the US, and Canada, I use sit-down toilet, not squat toilets, and I eat mostly with forks and knives, not with chopsticks or with my fingers.
Hundreds of millions of people in the areas you've mentioned have all the same characteristics as well.
>True that culture and wealth go hand-in-hand, but I think we're all more alike than different. I didn't like doing chores as a kid and I don't know a lot of Mexicans who did. We're more alike to those who self-apply and exclude us from the "Western" label than we are different.
Why try to be a member of a BS club that doesn't want you anyway? It's not as if being Western is any great achievement, that's just the way westerners use it when they laud themselves. With the rise of China, India, Brazil, and eventually Africa, the "West" is an increasingly insignificant part of the world. It just had a head start on plundering a new continent, and then the rest of the world -- which put it ahead of the rest of the planet for a while -- then again, Rome once was important too.