Yeah, the entire Romancing SaGa Series was skipped in the US, which was the SNES follow up of SaGa which did actually come here as Final Fantasy Legends.
I think Final Fantasy Adventure technically wasn't a total name change; IIRC, the full title of the game in Japan was something like "Final Fantasy: Seiken Densetsu" or so I heard, which is why there's stuff like Chocobos and Moogles in the game (Moogles managed to stay in later games, Chocobos...not so much.) They just removed the "Final Fantasy" in the title when the 2nd game came out, and just released that one here as "Secret of Mana" making the fact that the two games were of the same series confusing in the US! At least the "Mana" title stood consistent...
I think its also worth noting that FF12RW came out after a time that FF Sequels were not unheard of; before FFX-2, the only sequel was...that FF5 OVA, which apparently had almost nothing to do with FF5, outside of establishing it as being the same world, some ridiculous number of decades later so the relation is purely a setting one. So in reality, the idea of a true FF Sequel was indeed unheard of before FFX-2.