The concept of Jewishness hinges on the Chosen People idea.   

There is no nation, ethnicity or race that can be called the Chosen People today.   

God chooses people one at a time based on their choosing to believe and receive Jesus Christ - His physical manifestation ( Express Image).   

The core tenet of Christianness is expressed in the following -

There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for you are all one in Christ Jesus. Gal 3:28 There is no difference in us who are In Christ.      This statement is the broadest most inclusive statement that can be made regarding our Lord`s will for humanity.     We are not one in physical birth but we become one in the New Birth.      Seeing ourselves as New Spirit beings In Christ is critical for our fellowship with Him and others In Christ.

To be one In Christ is the privilege of every human being but it is only possible by Grace Through Faith in Jesus.   

There is a phrase in marriage ceremonies that goes something like this:
"Forsaking all others, cleave only to 'fill in the name'".   

When a person desires to be In Christ which is to enter into Spiritual Marriage with Him then they must of necessity "Forsake all others and cleave only to Christ Jesus."

To retain part or all of the Old Man is to deny the New Creature.   

I am not a white Christian.   
I am not an Irish Christian.   
I am not an American Christian.   
I am not a Protestant Christian.   
I am not a Pentecostal Christian.   
I am a Christian

Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new. 2Co 5:17 When we come to Christ Jesus in faith that He is Mighty God, Everlasting Father, Saviour and Lord we are born of His Holy Spirit.      At that point we are a New Creature.     We are super-human.     We are Sons Of The Holy Spirit.      But the new creation is hidden with Christ in the Holy Spirit.      The only way that it manifests is through a transformed mind.      We do not get the transformed mind at the point of faith.     We get it by absorbing the Word Of The Lord and meditating on it in the Holy Spirit.     We must then walk out that which is in our mind and heart.      Old things have passed away and all things have become new as far as the Lord is concerned, but we must forget the past and see ourselves as the Lord sees us for the effect of the old things to pass away from our minds and hearts.      We must choose to see all things as new in order to experience new things.