Great analogy, but not quite. It's more like the South seceded, then over the years became much more powerful, then in 1940 claimed that the North belonged to the South.
Like it, but how about the South not just seceded, but counter-attacked and drove what was left of the Union government to Puerto Rico from whence both 'countries' claimed sovereignty over the whole.
Eventually the Puerto Rican's US gets very successful within the scope of an island nation and the Confederate USA starts planning on taking PR back, but PR US has since made alliances with a global military power.
Eventually the Puerto Rican's US gets very successful within the scope of an island nation and the Confederate USA starts planning on taking PR back, but PR US has since made alliances with a global military power.