And where do those verses state that the individual Christians no longer have their salvation? True, those churches no longer exist, but that doesn't damn the individual Christians in them. That's a rather loose interpretation of those passages.
Salvation is a gift. It is freely given us for the asking by nothing more than God's mercy and desire to forgive. And He's going to renege just because once we're saved we continue to not live up to the standards He established?
He didn't let us not living up to His standard keep Him from doing everything in His power to save us in the beginning. He lived for us, He died for us, He calls us, He empowers us, He gives us the Holy Spirit, He determines the exact times and places where we live so that we will seek Him and perhaps reach out to Him and find Him, He convicts us of sin, righteousness, and judgment.
He does it all, short of making the final decision for us? And He's going to abandon us to hell because we don't live up to the standard He set?
NOBODY can live that kind of life. All our righteousness is as filthy rags in His sight.
The God who imparts the righteousness of Christ to us sees us as sinless as Christ when He looks at us. We are His beloved Bride? And he's going to throw us under the bus for what? Not going to mass Sunday morning? Giving into temptation on the spur of the moment?
Our lives may be somewhat righteous, just as the Pharisees were, but God looks at the heart. The human heart is deceitful above all else and desperately wicked. No one will ever make it according to Catholic doctrine.
That's why those of us who have thrown ourselves on the mercy of the court are sure of our salvation. God will not send His own children to hell for not being perfect. Otherwise heaven will be an awfully lonely place.
My children are my children regardless of what they do and nothing will ever keep me from loving them or cause me to disown them. They may break my heart some day by their behavior but I will not disown them.
In fact, if you adopt children, it would be impossible to un-adopt them...
And even if they did do something that, you in your humanness, caused you to disown them, they can never become unborn to you. They will always share your DNA and will forever be your biological offspring. With God, we are born into his family when we trust in Jesus Christ and receive him as our savior. We are indwelt with "spiritual DNA", his Holy Spirit, whereby we are sealed until the day we are redeemed in Heaven with him. There is nothing we CAN do to become unborn again.
Those who insist that we can wiggle out of his hand - the hand that Jesus said no one can pluck us out of or that he will never cast us out of - completely miss the point that he is holding onto us, we are not holding onto him. If we are born again/from above, then we cannot lose that condition and, if we could, then there would have to be reborn agains, re-reborn agains, re-re-reborn agains, etc. and there is nothing Scripturally that even comes close to saying that can happen. We can have the assurance of our salvation because that is how God INTENDS for us to live, not as scared step-kids or adoptees who can never be sure they will be kept in the family, but as true sons and daughters of the Most High, heirs of God and joint heirs of Jesus Christ - based on HIS grace and not of ourselves.