Steve Ray has a list of 35 loaded Questions for "Bible Christians" (quotation marks his)(link to the whole list). This is number 34/35. I'm trying to provide the answers in a common format, for easy reference.
34) If the unity of Christians was meant to convince the world that Jesus was sent by God, what does the ever-increasing fragmentation of Protestantism say to the world?
The premise of the question is mistaken. Denominational unity was not intended to convince the world that Jesus was sent by God.
1) See the answer to question 33, as well as my previous discussion of John 17 (link to John 17 discussion).
2) What ought to be remarkable to Rome's apologists is the continuity of brotherly love among the "ever-increasing fragmentation" in "Protestantism." Extremely few of those fragments (Westboro Baptists, for example) make the claim to be the one true church. The rest accept believers in other denominations as their brethren even despite the denominational disunity.