Well... lets run a thought experiment then.
Ah, but now you're not saying it's impossible that God could do the same thing to the Catholic Church that he did to Israel, namely, abandon it and carry the same spirit on as a "New Israel" or "New Church" in someone or something else. You're arguing that God has not because Protestantism, Islam etc. are all wrong, not that God could not or would not.
In other words you've left the possibility open of Christ leaving the Catholic Church. It's on this basis I'm speaking.
The principle is very simple: if someone turns away from God, God will turn away from them. If an organization turns away from God, God will abandon that organization (but not necessarily every individual member).
If someone commits murder or thievery or other crimes, then no one in their right mind would say "this person has Christ in them". It doesn't matter if the person says "I'm a Christian"- they're not. They don't have Jesus living in them. The proof of this is that they commit murder, thievery, adultery etc. So why should anyone listen to their preaching, no matter how vigorously they insist that they have Jesus?
So, if an organization commits similar crimes, no one in their right mind would say "this organization has Christ in it", no matter how vigorously it insists that it does.
There are no exceptions to this rule. Not Israel, not the Catholic Church, not Protestantism, none. But you're trying to argue that God somehow made an exception for the church and remained anyway? The Jews and Pharisees also tried to argue that they were somehow an exception to the rules- so should I become a Christian Zionist, then?
It seems more logical to say that God left the Catholic Church, but, like Israel and like the Jews, he will redeem it one day, Amen.
For that reason the gates of hell will not prevail against the Church, whether the spirit of that church is in the Jews or in the Gentiles or in the Catholics or in the Protestants or in someone else. The spirit of that church will always live on- there will always be those who are devout and believe in Jesus. They are the church, and that is more important than specific denominations or titles or claims to heritage.