The Amazon Brazil site is not automatically opened. According to the search results, for sellers who have already opened the US site, if they want to open the Brazilian site, they need to perform a series of operations, including selecting the Brazilian site in the background, setting deposit and payment account information, and using Amazon's official tools to synchronize product selection.

For sellers who have not opened Amazon, they can directly log in to the Amazon official website to register. In addition, Amazon also provides some convenient measures, such as supporting deposit methods of US bank cards or third-party payment tools, and providing official Listing upload services, etc., to help sellers open and operate the Brazilian site more smoothly.

Therefore, sellers need to follow Amazon's guidance and requirements and actively complete the relevant registration and setup process in order to successfully open the Brazilian site.