Rockstar is a US company, but the developers of GTA are Rockstar North in the UK. They used to be their own company developing GTA, when they were bought by Rockstar.
I have not played Red Dead but GTA is definitely not an RPG. It's an action adventure and at least from what I've seen from the former I'd expect it to be the same.
For an Action RPG, decision making, conversation options, and of course a skill trees are necessary. Basically you need to be able to shape your character to "play a role".
Generally, RPGs involve character progression through stats, and RDR really doesn't have that. It's an action adventure game with an emphasis on storytelling.
The publisher is but the studio that makes GTA games is in Scotland. Not sure about Red Dead. Probably a collaborative effort between their studios, most of which are in the UK.