Los usuarios de AMC tienen acceso a todas las instancias de AMC en una cuenta de forma predeterminada.

False. By default, users do not have access to all Amazon Marketing Cloud (AMC) instances within an account. Access to AMC instances is controlled through permissions, which are typically managed by an administrator. This ensures data security and allows organizations to restrict access based on roles and responsibilities. Each AMC instance can contain sensitive campaign data, so granular control over who can view or modify data within specific instances is crucial. If it were true, it would pose significant security and privacy risks.