The Samurai association is not so much related to the republic/empire story itself but to the genre of films that helped inspired it. Star Wars (like a lot of western movies at the time) has many chanbara influences (The sword fighting style in the first films, the Jedi robes, the imperial crest for e.g.) and Lucas has mentioned he was inspired by The Hidden Fortress which has a few common thematic elements.
So yes not a Samurai film, but a work inspired by chanbara/Samurai films with enough stylistic and thematic elements to be recognizable.
