I will post this answer even though there are better answers. This answer provides additional information on one particular design.
I have deployed multi-region WordPress on both AWS and Google Cloud. WordPress is simply not designed for this. Unless you have money to spend and IT talent, choose a company that offers distributed WordPress managed. You will save money and headaches.
For the last project, the company did not require instant updates/synchronization globally but required high traffic loads that could be predicted. We decided upon separate WordPress systems in each region. We wrote software that ran once per hour to synchronize the WordPress content between systems. This involved syncing the file system wp-uploads
directory, moving static assets to cloud storage behind a CDN and copying content changes to each MySQL database. If there was a conflict, an email was sent to an admin to manually review. Once per day software ran that compared the newest posts to verify content and synchronization between servers.
The systems in each region were load-balanced and auto-scaled. The database was hosted separately on managed MySQL servers. The WordPress directory was hosted on an NFS share. We used cloud storage + CDN for static assets (css, js, images, downloads). Except for cloud storage, we did not share assets between regions. Each region was independent. Each region has at least two servers running at all times. During forcasted peak loads (marketing releases, events, etc.) we would scale up/down each group based on timezone via a GUI click to prewarm the systems.