I saw that one. In a way, I like it, but I was thinking without intervention of a time traveller, what could have happened? In the times, the republic wasn't in the mood to accept foreigners and non-whites

Just looking at the history of the Americas as I've read, it would be far more likely to go north, into the Caribbean, and west, and perhaps take more land from Mexico in the Mex-American War, and have a border that parallels roughly the tip of Baja California. Perhaps rename the gulf to "Gulf of Florida" or "Gulf of Texas" in that timeline...
James