Is or was Judas Iscariot one of all Israel?
Judas Iscariot was a Hebrew in covenant with God. Jesus called him along with the other eleven disciples and "named them apostles."
If Jesus named the twelve men He chose as apostles, then these men are apostles. Jesus called them apostles and I do not contradict Jesus. Like Peter, James, and John and the others Judas was an apostle of the lamb who was a disciple of the Lord called in the same capacity as the other disciples.
12 And it came to pass in those days, that he went out into a mountain to pray,
and continued all night in prayer to God.
13
And when it was day, he called unto him his disciples: and of them he chose twelve, whom also he named apostles;
14 Simon, (whom he also named Peter,) and Andrew his brother, James and John, Philip and Bartholomew,
15 Matthew and Thomas, James the son of Alphaeus, and Simon called Zelotes,
16 And Judas the brother of James, and
Judas Iscariot, which also was the traitor. Luke 6:12–16.
Born in Kerioth, Israel, specifically in the land of Judah, Judas was a man like all men under the Law and when the high priest sacrificed yearly an animal for the sins of God's people, then for one year their sins were covered until the next year and the next year after that. Then, there came the lamb
of God who under the Law sacrificed Himself finally and eternally for the sins of God's people under the Law. Jesus died for the sins of God's people. God's people are those who are Abraham's seed and heirs of his promises.
Everyone betrayed Jesus. Everyone rejected Jesus at a time He needed them the most and all forsook Him to save their own lives. But Judas declared Him. Judas led men into the night and pointed Him out and said, "This is the man. This is Jesus the Christ whom you seek."
The bottom line is that Jesus came to Israel as promised and came to save Israel with the sacrifice of Himself for their sins. And this He did. As Saul says:
4 But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law,
5
To redeem them that were under the law, that we might receive the adoption of sons. Galatians 4:4–5.
Israel's redemption is complete. God has sent forth His Son to die - and resurrect - for the sins of the children of Israel under the Law of God. God saves Israel. Israel does not save themselves. As the hymn says: "Nothing to the cross I bring, surely to the cross I cling."
As Jonah says, "Salvation is OF THE LORD."