It was always a fun fact to me that the majority of the original Red Dead Redemption map was ported over to its sequel, or at least on the American side of the border, but notable in it's absence was Mexico, which wasn't included, even though parts of it are still visible from a distance within Red Dead 2.
Mexico was a huge part of the original Red Dead Redemption and serves a big chunk of the game's story. It's even weirder to think though that parts of Mexico already do exist in Red Dead 2, and some Red Dead Online players have even found themselves spawning there by random chance from time to time. It's speculated that it may return as part of a future Online update, but in the meantime, modders are working hard to restore the region to single-player mode.
The new mod pack from Siemreaper collects together all the best mods that restore Mexico into the game, and the result is a huge, lore-friendly restoration of the region into the game, including a new bridge to get you over there.
The pack makes the installation of the various mods easier to handle, although it does require you to install a few extras, such as Lenny's Mod Loader and Script Hook for RDR2 to get it all working correctly.
Several settlements from the Red Dead 1 Mexico map have been restored here, and it's great to explore around. That's the limit of it right now though, with no missions or gameplay, and certainly no support for online, it's more of curiosity right now. Still, I've found it really nostalgic to wander around and rediscover some classic locales from the original.
You can download the Mexico mod pack here.