I don't know why someone would tell you that Star Wars was an homage to The Seven Samurai. Their stories are very different. SS is about a village being terrorized by bandits and recruiting a motley group of defenders who teach them how to defend themselves.
Beats me, since I've never seen Seven Samurai
. But I've been hearing and reading it for decades. A quick Google search came up with a bunch of references, including this one.
As for the definition of "Western," it's true that nominally it refers to a story taking place in the American West during the frontier era, but I think that's taking it too literally. After all, the version of the American West seen in movies and TV never really existed; it's a mythology created by the makers of motion pictures. So in a way that makes it timeless, a set of storytelling symbols and tropes that don't literally correspond to a specific place or time and thus can be mapped onto other settings.
Like anything else, a Western can be stylized, mythologized or realistic. You can map the tropes onto another genre, but it doesn't take the genre with it. You could tell the same basic story as High Noon
in ancient Herculaneum, but it would be silly to call that a Western.