Pretty sure the 50% Chinese sellers is more like 80%, including those who use USA addresses in Florida...

But this says it all..(not that it is news)

“[T]he risky downside to this is that US and EU based sellers do not find this avalanche of China based sellers very amusing,” former Amazon executive Sebastian Gunningham once told colleagues in a 2015 email as the company was ramping up its recruiting in China, adding, “I have coached the team to be aggressive marketing in China to sell globally,” but to be “low key” about the influx of Chinese sellers in Western markets.

adding millions of new merchants over the years has also helped to line Amazon’s coffers in the form of revenue from seller fees. In fact, if Amazon’s third-party seller business were its own company, it would be a Fortune 25 corporation. In 2024, seller fees filled Amazon’s war chest with more than $150 billion in revenue—and that doesn’t even include the billions more in advertising that independent merchants buy on the world’s largest marketplace.