From reading this it seems like you think 'China' was mostly peaceful, which is laughably false. China in the sense that most people think of it never really existed until modern times. It is a land area the size of Europe, and was conquered over and over again by mostly internal and some external forces. Saying that they weren't expansionist is just completely false. Pretty much every chinese dynasty started off by trying to conquor what was tradional china, and most of them never even fully managed that. And when they did manage it the territory they controlled was so huge they couldn't really handle governing more than that.
I really want to know how the west was much more expansionist cirque the 15th century, cause so far as I can remember the west was much more polarized into set borders at that time than china was. I think your view of history is a little too clean, history and the evolution of warfare is much more chaotic than that, especially with regards to major inventions. It was also largely coincidence that gunpowder at the time allowed the turks to finally take constantinople. Those turks benefited from the fact that they happened to be the attacking a walled city at the time when a new technology to attack walled cities was really gaining steam.
By the late 16th century Europe had outpaced everyone else developing that tech, for a whole lot of reasons, none of which really had much to do with Europeans being more or less expansionist than anyone else.
Did I say they were "mostly peaceful"?
No?
Then you might not want to phrase your argument predicated on a statement I did not make. We call that a strawman.
What I said was
Eh China never had a need to invent guns because they never really invaded land outside their territories for the greater part of their history after the Warring States period.
They weren't expansionist.
Not being expansionist outside of East Asia/traditional territories going back thousands of years =/= by necessity peaceful in all occassions and at all points in time. How you made that leap I'm not really sure, but what it tells me is you're reading what you want to read in what I said, not what I said. I was specifically referring to the fact that Chinese didn't start loading up their boats and marching on Africa and the Americas and Europe, attempting to settle them as Han Chinese or Mongol lands or what have you, not about their internal relations.
Then you ask how the west was more expansionist in the 15th century than China. Well let's see, the Mandarins were busy running one of the most successful bureaucracies in history in China while Europeans were laying the foundation for colonialism, how is this even up for debate? The borders within Europe proper are irrelevant to this discussion, a red herring fundamentally because we're talking about European actions outside of Europe, not within, so that goes back to your original strawmanning of my statement.
For all these questions about why Europe and not some other continent I highly suggest readingGuns, Germs, and Steelby Jared Diamond
Its a good read, but a lot of anthropologists and archaeologists feel he oversimplifies things with his heavy focus on geography. Cultural adaptations can and are often separate from environmental adaptations, and trying to explain every difference in human societies as heavily founded in geography is a bit flawed. Environment definitely play a big role, but how a culture adapts to an environment can vary quite broadly. A good example is just take any two groups in Africa living side by side. Their entire ways of existence can vary dramatically. Maybe one group is pastoralist, another agriculturalist, maybe one group practices ancestor worship, another believes in monotheism. Maybe one group lives entirely off products made by their herd animals, blood and milk and urine and meat, what have you, while another lives harvesting exclusively Mongongo nuts.
Boiling it all down as adaptations to environment ignores the cultural impact. Its somewhat akin to saying that genetics are the only thing that defines people's personalities, even though we know epigenetics, culture, world view, class status/social standing, etc can all impact behavior and personality.