Contradiction with Matthew 15:24
Jesus stated that He was sent only to the lost sheep of the house of Israel, while James 1:1 refers to outreach to Jewish Christians scattered abroad.
Matthew 15:24: But he answered and said, I am not sent but unto the lost sheep of the house of Israel.
Contradiction with Acts 10:45
The Gentiles received the Holy Spirit, showing outreach beyond just the twelve tribes of Israel, unlike James 1:1 which is addressed solely to them.
Acts 10:45: And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.