Why don't Christians call themselves Jesusians?

Christ isn't a surname, it's an epithet. It means "The Anointed" in Greek. Greek was a lingua franca in those days, a great many people spoke it or at least knew some, so it's not surprising that the word became the origin of the religion's name. It also worked better than "Yeshua" or "Jesus".

It's not a surname, it's a title.

We see Jesus as more than a wise teacher who might make mistakes. We see him as the accomplishment of the promise of God to be with his people. He is messiah, Christ being the Greek equivalent.

Christ is a title, not a surname. Surnames were it used until the 16th(?) century in English speaking countries. If there was more than one Jesus in the room he would be referred to as Jesus of Nazareth. In Nazareth he would be called Jesus son of Joseph.

Jesus was a common name, and still is in the Latino world. It wouldn't be distinguishable enough.

Because it's not a surname....

Because "United Church of Jesus" sounds like a Mexican soccer team rather than an actual church.

Christ is not a name but means that Jesus is the Messiah=Christ means the anointed one, Jesus means savior

If there was a jesus, he never was called jesus christ in his life, that is just the Hellenization of his real name.

Christ is not a name it is a title like savior or redeemer. Jesus was his name, Christ was what he was.