Just a point of context - you're looking back at Bach from a historical vantage point where he's been gobbled up and lumped together with the entirety of "western culture".

To his contemporaries, he was a member of a specific national "culture", and influenced by the greats of other European (and non-European) cultures of the time.

Different cultures have access and then value different cultural expressions. Asking why there isn't the japanese Bach is a bit like asking why there is no spanish Lee Changho

You could make the argument of how elaborate is a piece of art but in the case of individuals like that they are so far off from the median person in their culture that it'd be quite hard to see their achievement as coming from their culture instead of their own cognitive abilities. The societies they grew into either fought them or allowed them to strive but that's about it.

I’m a poor student of music and history but my opinion:

Europe was a civilization in a perpetual state of war with power rarely concentrated, so even concentrated wealth was local and therefor still distributed amongst different kingdoms and nobles.

This means more opportunity and support: One village/patron/noble/king doesn’t like your style? Go travel and find someone else to sponsor you.

I don’t think this was possible elsewhere. East Asia for example—thanks in part to Confucianism—had China dwarfing most of the region, with a stifling top down meritocracy.

And today, China and the United States have incredible sway over the globe I imagine things are stalled.

Different cultures have different florescences. Where are the other cultures when Egypt invented hieroglyphics, where were the other cultures, when the Greek were philosophizing, where were the other cultures, when the Mayas flourished. Where were the other cultures, when the Romans played with rethoric. What were the other cultures doing when the Chinese culture flourished.

Also these are not really competing, but more like morphing into another. During the Antique there was trade with India and China, subsahara parts of Africa. The Arabian mathematics was preserved in Greek literature. This was then rediscovered and translated into Latin, which kick-started European philosophy and sciences.

The same is true for religion. Christianity is the mix of Jewry and Greek philosophy. The Greek were heavy influenced from the Egypt culture. The Jews took their knowledge from the Arab peoples in their regions and also part from Egypt. This Monotheism came from earlier Polytheism and earlier natural religions.

I would maybe look at this a bit differently.

Where are the great classical artists in even the rest of Europe? The great classical composers of the 18th century were all German and all made their careers in Vienna, Austria in the 1700s. This was where you wanted to be. Its like the musical equivalent of silicon valley in the 2000s. Vienna was among the wealthiest cities in the world. Habsburg nobility had an unusual fascination with funding arts and culture. Spurs competition to push the art to its limit, in hopes of attracting the wealthiest backers. Budding industrial revolution make the production of complicated musical instruments more viable.

Your argument is ignoring musical geniuses such as Vivaldi, Chopin, Rachmaninoff, none of them came from Vienna or Germany.

In addition to the sibling comment https://news.ycombinator.com/item?id=46012832, German(y) wasn't a state back than but a much larger common cultural term. People living in different parts of Europe would understand themself to be German, even if they wouldn't be considered to be now by their ancestry. It was simply the cultural lingua franca of Central Europe at that time, the countries were smaller and quite numerous. People used to speak German in the same way as they now speak English.

I think the mobility at that time is underestimated, it was very common to relocate to a place where the innovation happens and the other great minds were. It was more common to tour through Europe as part of the Education, than it is now. Sure a journey would take a week instead of a few hours, but you also don't relocate every day.