You actually didn’t post the end of John 17:21 “that the world may believe that thou hast sent me.”
If Christians are one “that the world may believe that [the Father] hast sent” Christ . . . that doesn’t somehow make you a God. It makes a Christian part of the Church and a unified church provides consistent and more persuasive witness. The fractured church offers poorer witness than it should.
Regarding interpretation of the Bible, I’ve noticed that Mormon’s, from a Christian understanding, cherry-pick verses with strange results. A Bible that asserts there is one God hundreds of times turns into a polytheistic scripture, according to a Mormon, based on Psalm 82, and a wild (and easily apparent) misreading of the verse.
And you still haven’t addressed the meat of the scripture that says our “oneness” is the same “oneness” that is shared by God and Christ. If you want to slap your hands over your eyes and ears and then flit to the next verse, that’s your problem not mine.