Beginning with Abraham, we read, "and through your offspring all nations on earth will be blessed because you have obeyed Me." (Genesis 22:18) Abraham was most certainly a righteous man. He had been tested and proven worthy of that description. But did God speak to him that way because Abraham was somehow so good that God owed him something? Or, was Abraham the very best available choice for fulfilling a role in a process that had been set in motion long before? Was Abraham "the best man for the job"?
The promise continued through Abraham's son Isaac, and then through Isaac's son Jacob. With Jacob the process accelerated and expanded. God changed Jacob's name to Israel, and from his 12 sons began the 12 tribes of Israel, the Israelites.
Among Israel's 12 sons was Judah. From his name, his descendants became known as Jews. Abraham was not a Jew. Isaac was not a Jew. Judah's 11 brothers were not Jews. They were all Israelites, but only Judah's children and descendants, right to this day, are actually qualified to be called Jews. It's more than identifying a correct name, it's a matter of identifying the correct line.
All of Israel's 12 tribes would eventually have a great effect upon the world, 11 of them through exploration, wealth, and industry (especially Ephraim and Manasseh, the sons of Israel's son Joseph), and 1, Judah, the Jews, the selected line through which a Savior would be born -
"The scepter will not depart from Judah, nor the ruler's staff from between his feet, until He comes to Whom it belongs, and the obedience of the nations is His." (Genesis 49:10)
Fact Finder: Was Jesus Christ descended from Judah?
Matthew 1:1-3, 27:11