What cultures, if any (besides Ancient Egypt), believe(d) that the stars are other worlds/lands/islands?
Judaism, according to one interpretation in the Talmud of the verse in Judges 5:23:
"“Curse Meroz!” said the angel of the LORD. “Bitterly curse its inhabitants, Because they came not to the aid of the LORD, To the aid of the LORD among the warriors.”"
"...As it is written: “Curse bitterly its inhabitants” (Judges 5:23), in reference to all those sitting together with Meroz...And Ulla said: Barak ostracized Meroz with the blowing of four hundred shofarot due to his failure to come. As for the identification of Meroz, some say that he was a great man and that he was ostracized because he did not join in the war effort. And others say that the reference is to a star and not a human being, and that it did not aid the Jewish people in their battle, as it is stated: “The stars fought from heaven; in their courses they fought against Sisera,” (Judges 5:20). This star, which did not help the Jewish people, was cursed." (Tractate Mo'ed Katan, 16a)