If Melchizedek was Shem, son of Noah, then Canaanite Jebusites must have conquered Salem between Abraham and Joshua.
https://www.aish.com/atr/Where-Was-Salem.html
… In fact the Sages identify Salem (“Shalaim”) as none other than the holiest city in the world, Jerusalem (Targum, Bereishit Rabbah 56:16; see also Psalms 76:3 where Salem is used in reference to Zion). The Sages also identify its king Melchizedek as none other than Shem, the son of Noah (Targum Yonatan, Targum Yerushalmi, Talmud Nedarim 32b).
(Melchizedek was more a royal title than a personal name, similar to the titles Pharaoh and Abimelech. See Joshua 10:1, where the king of Jerusalem is similarly referred to as Adonizedek. The commentators, with some variation, understand Melchizedek to mean “king of the place of righteousness.”)…
Canaanites were and are also Semites and also spoke various Semitic languages related to Hebrew