Think of multisite as many blogs with separate content all bundled under one domain name, as in www.example.com/blog1 and www.example.com/blog2 . Each has their own content in the same database.
Blog1 has content, Blog2 has content, but you can’t see Blog1 content in Blog2. So a multisite will not work without significant changes…
…which you are going to have to do anyway. You will need to create a template that can display variable content from a separate database table. The template would display the basic stuff for a page/post, then have code that would select content specific to the region.
There may be plugins that will let you do this, but this place doesn’t recommend plugins…