Just because a driving instructor says you have poor depth perception doesn't mean it is true. That requires a more advanced method of diagnosing than what the average driving instructor is capable of (if the instructor were capable of it then she would not be a driving instructor).
It is actually possible that you were correct and you did have enough clearance. It makes me wonder why the instructor wasn't doing her job well enough to warn you in advance that you might not have enough room. She could have caused an accident by jerking the wheel. Remember the old saying: "those who can't (do it)... teach."
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The Rhymin' Red Rover, that's what they call me,
Too old for a sailin', too young fo' the sea;
Set sail fo' a sunset, to a land that is free,
I'm the Rhymin' Red Rover, and that's where I'll be.