Show me one scripture that says you will lose your salvation if you leave the Catholic church.
While I could reply, you did not answer the questions.
Here is my answer to your question.
Jesus delegated to His Catholic Church and its leaders to “bind and loose” Mt 16:18-19
“If man has a hundred sheep, and one of them has gone astray,...does he not go in search of the one that went astray.” If he refuses to listen to the Church, let him be to you as a Gentile and a tax collector.”
“Truly I say to you , whatever you bind on earth shall be bound in Heaven.” MT 18:15-18
Also read the Catholic Catechism 846 - 848 “Outside the Church there is no salvation”. Christ gave His Catholic Church the authority to “bind and loose”.
The Catholic Church teaches infallibly, “extra ecclesiam nulla salus,” or, “outside the Church there is no salvation.” But as with all dogmas of the Faith, this has to be qualified and understood properly. The Catechism of the Catholic Church lays out the truth of the matter succinctly in paragraphs 846-848, but I would recommend backing up to CCC 830 for a context that will help in understanding these three essential points concerning this teaching:
1. There is no salvation apart from Christ and his One, Holy, Catholic, and Apostolic Church. Again, this is an infallible teaching and not up for debate among Catholics.
2. Those who are “invincibly” ignorant concerning the truth of #1 above will not be culpable for this lack of knowledge before God.
3.Those in the category of #2 have the real possibility of salvation even if they never come to an explicit knowledge of Christ and/or his Church.
These make very clear that anyone who is ever saved is not saved by his or her false religious beliefs.
The point of the parable of the prodigal son (Luke 15:11–32). In this parable, the father of the family represents God, and one of his sons leaves the family and embarks on a life of sin. Yet he repents and is welcomed back by the father, who declares that the son “was dead, and is alive; he was lost, and is found” (v. 32).
The Catholic Church was founded by Jesus Christ and He is still the Head of the Church. All other churches were founded by men or women.