While I certainly agree that there are certain Scriptures that pertain to the Jewish Nation alone…such as Roman’s 9-11...and Revelation 4-22...which pertains to Israel and all unbelievers...but that's another topic.
God chose for Himself a people through which to teach all peoples…not to mention the heavenly beings as well. A people through which He would reveal Himself as well as reveal the depravity of our sin nature and rebellion toward God.
However, all Scripture can be applied to Gentiles as well as we learn from the example of Israel. We as Gentiles, have been grafted in…rightful heirs by adoption.
Rom 11:16 For if the firstfruit is holy, the lump is also holy; and if the root is holy, so are the branches.
Rom 11:17 And if some of the branches were broken off, and you, being a wild olive tree, were grafted in among them, and with them became a partaker of the root and fatness of the olive tree,
Rom 11:18 do not boast against the branches. But if you do boast, remember that you do not support the root, but the root supports you.
Rom 11:19 You will say then, "Branches were broken off that I might be grafted in."
Rom 11:20 Well said. Because of unbelief they were broken off, and you stand by faith. Do not be haughty, but fear.
Eph 1:4 just as He chose us in Him before the foundation of the world, that we should be holy and without blame before Him in love,
Eph 1:5 having predestined us to adoption as sons by Jesus Christ to Himself, according to the good pleasure of His will,
Eph 1:6 to the praise of the glory of His grace, by which He made us accepted in the Beloved.
Gal 3:26 For you are all sons of God through faith in Christ Jesus.
Gal 3:27 For as many of you as were baptized into Christ have put on Christ.
Gal 3:28 There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female; for you are all one in Christ Jesus.
Gal 3:29 And if you are Christ's, then you are Abraham's seed, and heirs according to the promise.
And regarding these particular verses:
Joh 15:18 "If the world hates you, you know that it hated Me before it hated you.
Joh 15:19 If you were of the world, the world would love its own. Yet because you are not of the world, but I chose you out of the world, therefore the world hates you.
Jesus is speaking not only to the Jews in His presence…or regarding the world as it was known during His earthly ministry…but to all who are in Christ Jesus….His disciples.
Note Jesus praying in the Garden of Gethsemane.
Jesus prays for His Disciples…then prays for all Believers:
Joh 17:14 I have given them Your word; and the world has hated them because they are not of the world, just as I am not of the world.
Joh 17:15 I do not pray that You should take them out of the world, but that You should keep them from the evil one.
Joh 17:16 They are not of the world, just as I am not of the world.
Joh 17:17 Sanctify them by Your truth. Your word is truth.
Joh 17:18 As You sent Me into the world, I also have sent them into the world.
Joh 17:19 And for their sakes I sanctify Myself, that they also may be sanctified by the truth.
Joh 17:20 "I do not pray for these alone, but also for those who will believe in Me through their word;
Joh 17:21 that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me.
Joh 17:22 And the glory which You gave Me I have given them, that they may be one just as We are one:
Joh 17:23 I in them, and You in Me; that they may be made perfect in one, and that the world may know that You have sent Me, and have loved them as You have loved Me.
I’m hard pressed to consider this Scripture is not speaking of ALL Believers…especially considering the eternal nature of God...who knew each of us before the foundations even.
Anyone who is in Christ Jesus, will be hated by the world…because we are not of the world…just as our Lord is not of the world....and the world loves it’s own.
Joh 3:19 And this is the condemnation, that the light has come into the world, and men loved darkness rather than light, because their deeds were evil.
Joh 3:20 For everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed.