Amazon already reached these 12 marketplaces:
USA, Canada, Mexcio, UK, Germany, France, Italy, Spain, Japan, China, India, and Australia.
They use similar/the same platform across all marketplaces, that’s why, it would be easy for you to use different marketplaces once you master one.
Also, they have the resources to break through in each market. So, there are more marketplaces to come as they expand.