What is a true Christian? Wasn't the Catholic church around much longer than anyone other than the Jewish?

Just wondering, because according to History, the only reason why Born agains, Methodists, Baptists, ie Protestants exist is because King Henry the 8th was not allowed to divorce one of his wives (this was before he decided beheading them was easier), so he went and started the church of England, which eventually broke off into all the other branches of Religion. So why do people in those religions call themselves True Christians?