To understand this answer, we will look at just two aspects.
One, Christ speaks literally about many things many times, yet no one believes He turned into a literal door or into a nebulous ghost of a concept like truth.
Two, Protestants disagree with transubstantiation not because they don't believe the bible, but because they believe that Christ's sacrifice was done once for all time.
When Christ said, I am the way, life, truth, what did those three things look like? What ghost can one conjour to represent truth? Rather, they looked stedfastly at Christ who was clearly standing there in front of them.
Jesus saith unto him, I am the way, the truth, and the life: no man
cometh unto the Father, but by me.
When Jesus said, I am the door or you are a sheep, do you take this literally? Is He wood, rock, blanket, or what as that literal door?
Then said Jesus unto them again, Verily, verily, I say unto you, I am the door of the sheep.
So likewise when Jesus said this, did He disappear and become a loaf of bread?
And as they were eating, Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take, eat; this is my body.
So, it is clear enough that Christ speaks specifically at all times, but that is not to say literally at all times.
With lovely irony, when the bible does literally say Christ sat down as an offering priest because of His own one sacrifice, Protestants believe this, while Roman Catholics do not.
But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God;
There is no priest presuming to be Christ on earth who offers the "same" sacrifice that Christ did some 2,000 years ago.
Though time wouldn't permit, it is interesting enough to view this contrast between the two views of a literal piece of bread and a literal ongoing sacrifice done daily versus a metaphor and one sacrifice of Christ's body done once for all time.
So for Protestants, the plain words of Christ about this is My body and what it represents are clear enough.