Steve Ray has a list of more than 35 loaded Questions for "Bible Christians" (quotation marks his)(link to the whole list). I originally planned to respond to just 35 of them, but the series seems to have been of interest, so in this extension, I'm responding to three more numbered questions in his list, plus fourteen "bonus questions" that take the form "Where does the Bible say ... ." I'm trying to provide the answers in the same common format as the original series, for easy reference. This is number 16/17.
Where does the Bible . . .
. . . that Protestants can have an invisible unity when Jesus expected a visible unity to be seen by the world (see John 17)?
1) John 17 says nothing about denominational unity.
2) The unity John 17 is talking about is a unity of love.
3) While love itself is invisible, that love exists among "Protestants" and is seen by the world.
The ultimate fulfillment of Christ's prayers in John 17 will be fulfilled in heaven. There are shortcomings of love on earth, and sometimes those shortcomings can be expressed denominationally. That is very sad, and "Protestants" should work to remedy those shortcomings. Nevertheless, the many fraternal relations that exist among denominations help to demonstrate that denominational boundaries do not necessitate any lack of love.
See also the more detailed discussion of John 17 at the following link: (link).