The seven epistles to the seven churches in Revelation 2 and 3 are full of references to the old testament, which the gentiles or believers out of gentiles (Revelation 1:4 tells us that all seven churches were geographically located in the gentile land of Asia, which is modern day western Turkey) couldn't have properly understood unless they were familiar with the Old Testament Scriptures:
To him that overcometh will I give to eat of the tree of life, which is in the midst of the paradise of God (KJV, Revelation 2:7)
... thou hast there them that hold the doctrine of Balaam, who taught Balac to cast a stumblingblock before the children of Israel, to eat things sacrificed unto idols, and to commit fornication (KJV, Revelation 2:14)
To him that overcometh will I give to eat of the hidden manna (KJV, Revelation 2:17)
thou sufferest that woman Jezebel, which calleth herself a prophetess, to teach and to seduce my servants to commit fornication, and to eat things sacrificed unto idols (KJV, Revelation 2:20)
... to him will I give power over the nations, And he shall rule them with a rod of iron; as the vessels of a potter shall they be broken to shivers (KJV, Revelation 2:26-27)
He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life (KJV, Revelation 3:5)
Him that overcometh will I make a pillar in the temple of my God, and he shall go no more out: and I will write upon him the name of my God, and the name of the city of my God, which is new Jerusalem, which cometh down out of heaven from my God: and I will write upon him my new name (KJV, Revelation 3:12)
As many as I love, I rebuke and chasten: be zealous therefore, and repent (KJV, Revelation 3:19)
So, given the fact that the word for "church" here can mean merely a congregation or gathering, could it be so that the seven epistles are in fact addressed exclusively to the Jews living in Asia, rather than to all Christians living in those cities - just like the Hebrews is also addressed specifically to the Jews, rather than to all Christians?