The Gospels do not support the idea of Jesus bringing the good news of the Kingdom to Jews only. In John 15 - if you read further, the faith of the Gentile Woman brings healing to her daughter. This was indeed good news. So the answer to His question in Matt 15:24 was NO and this was confirmed by His actions.
Jesus was testing her faith.
Jesus never contradicts Himself.
Jesus granted her the healing because she was willing to submit herself to the Jews, recall what she said about dogs eating the crumbs that fall from the Jewish children's table?
The gospel of the kingdom was always meant for Jews only. Take what the high priest Zechariah declared under the inspiration of the Holy Spirit in Luke 1
67 And his father Zacharias was filled with the Holy Ghost, and prophesied, saying,
68 Blessed be the
Lord God of Israel; for he hath visited and redeemed
his people,
69 And hath raised up an horn of salvation for
us in the house of his servant David;
70 As he spake by the mouth of his holy prophets, which have been since the world began:
71 That
we should be saved from our enemies, and from the hand of all that hate us;
72 To perform the mercy
promised to our fathers, and to remember
his holy covenant;
73 The oath which he sware to
our father Abraham,
74 That he would grant unto us, that we being delivered out of the hand of our enemies might serve him without fear,
You see all the Israel, all the David, all the "his people" everywhere throughout?
I understand its difficult for most of us to accept this revelation if we are only hearing it for the first time.
Many churches love to preach almost exclusively from the 4 gospels and to realize that Jesus was only sent to the lost sheep of the house of israel during his earthly ministry will indeed be shocking.
But no worries, the ascended Christ saved Paul to reach out to us gentiles. Christ had a plan for us from the very beginning. (Ephesians 3:6-9)