Is salvation only for the Jews? No….what about the Gentiles?
We know that God only gave Israel the law and they were guilty of breaking the law.
But what about the Gentiles? How are they sinners?
What law did they break?
When God created Adam, he sinned and therefore death came to the human race, because all of us sin, even though we did not break an explicit commandment like Adam.

Romans 5 “12 Therefore, just as sin entered the world through one man, and death through sin, and in this way death came to all people, because all sinned— 13 To be sure, sin was in the world before the law was given, but sin is not charged against anyone’s account where there is no law. 14 Nevertheless, death reigned from the time of Adam to the time of Moses, even over those who did not sin by breaking a command, as did Adam, who is a pattern of the one to come.”

The world at the time after Adam consisted of all the nations who were Gentiles, worshipping their own gods.
They were still sinners even if they did not receive any law.
The proof is that people have died ever since the fall of Adam.
Romans 6 “the wages of sin is death…”

God did judge the Gentile nations like Sodom & Gomorrah, the flood upon the world during Noah’s time. Those were temporary judgments that were foreshadows of the final judgment to come in the future.
Paul wrote that God judges Gentiles not based on the written law but based on the guilt of their conscience:

Romans 2 “12 All who sin apart from the law will also perish apart from the law, and all who sin under the law will be judged by the law…..(Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law. 15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.) 16 This will take place on the day when God judges people’s secrets through Jesus Christ, as my gospel declares.”

Gentiles in all nations know what it means to have guilt in their hearts. They know it is wrong to kill or steal because of their conscience.
After the flood, the nations were in the world, but still sinners who died.
Out of the nations, God called Abraham.
He responded in faith and believed in God.
Abraham became righteous by faith in Genesis 15.
God made a covenant with Abraham and his descendants.
The sign of the covenant was circumcision (Genesis 17)
All the rest of the nations were Gentiles (uncircumcised) who were dead in sin.

Colossians 2 “13 When you were dead in your sins and in the uncircumcision of your flesh”

Abraham’s descendants were the 12 tribes of Israel.
God gave the law to Israel to magnify their sins and make sin utterly sinful – the law increased sin and sin-consciousness!

Galatians 3 “19 Why, then, was the law given at all? It was added because of transgressions until the Seed to whom the promise referred had come. “

Romans 7 “7 What shall we say, then? Is the law sinful? Certainly not! Nevertheless, I would not have known what sin was had it not been for the law. For I would not have known what coveting really was if the law had not said, “You shall not covet.” 8 But sin, seizing the opportunity afforded by the commandment, produced in me every kind of coveting. For apart from the law, sin was dead.”

This is why the law is called the ministry of death and condemnation.

2nd Corinthians 3 “7 Now if the ministry that brought death, which was engraved in letters on stone, came with glory, so that the Israelites could not look steadily at the face of Moses because of its glory, transitory though it was, 8 will not the ministry of the Spirit be even more glorious? 9 If the ministry that brought condemnation was glorious, how much more glorious is the ministry that brings righteousness!”

The entire world was guilty – both Jew and Gentile.

Romans 3 “For we have already made the charge that Jews and Gentiles alike are all under the power of sin. 10 As it is written:
“There is no one righteous, not even one;….
19 Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be silenced and the whole world held accountable to God. 20 Therefore no one will be declared righteous in God’s sight by the works of the law; rather, through the law we become conscious of our sin.”
Romans 3:23 “There is no difference between Jew and Gentile, for all have sinned and fall short of the glory of God,”

The Jews were guilty of breaking the 613 commandments under the law.
The Gentiles were guilty of being outside the covenant (uncircumcised) and also guilty due to the conscience that accuses them of sin.
The entire world was under the sentence of the law.
The Jews could not become righteous by the law.
The Gentiles could not become righteous because they were outside the law.
The Gentiles were dead outside the law, outside the covenant, without God, having no hope in this world.

Ephesians 2 “11 Therefore, remember that formerly you who are Gentiles by birth and called “uncircumcised” by those who call themselves “the circumcision” (which is done in the body by human hands)— 12 remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world. 13 But now in Christ Jesus you who once were far away have been brought near by the blood of Christ.”

All were dead in sin, needing salvation!
This is why Jesus Christ came to bring salvation to both Jew and Gentile, equally, by grace through faith to all who believe.

Romans 3 “21 But now apart from the law the righteousness of God has been made known, to which the Law and the Prophets testify. 22 This righteousness is given through faith in Jesus Christ to all who believe. There is no difference between Jew and Gentile, 23 for all have sinned and fall short of the glory of God, 24 and all are justified freely by his grace through the redemption that came by Christ Jesus. 25 God presented Christ as a sacrifice of atonement, through the shedding of his blood—to be received by faith”

This is why the Gospel says that salvation is a free gift.
We are made Righteous by faith in Christ, apart from works.

Romans 4 “4 Now to the one who works, wages are not credited as a gift but as an obligation. 5 However, to the one who does not work but trusts God who justifies the ungodly, their faith is credited as righteousness….. for us, to whom God will credit righteousness—for us who believe in him who raised Jesus our Lord from the dead. 25 He was delivered over to death for our sins and was raised to life for our justification.”