Is saying, "The Christian religion is trivial," then correcting it to, "The Christian religion as practiced by Christians today is trivial, not what Allah revealed to our master Jesus," while seeking forgiveness, considered disbelief (kufr)?

There is no sin upon you for what you said, because what is meant is the false religion of the Christians, not the true religion of Jesus, peace be upon him. Allah has not approved for His servants any religion other than Islam, which is the religion of all prophets, including Jesus, peace be upon him, who called his people to the Oneness of Allah. And His, the Almighty's, saying: "When Jesus perceived disbelief from them, he said, 'Who are my supporters for Allah?' The disciples said, 'We are supporters for Allah. We have believed in Allah, and testify that we are Muslims.'" And the Muslims are the true followers of Jesus, peace be upon him, and when he descends at the end of time, he will follow the Sharia of the Prophet Muhammad, peace and blessings be upon him.