The shuttle reaches those speeds at an altitude where the air is too thin to sustain traditional flight. The blackbird can't possibly fly high enough to reach those speeds for 3 reasons. 1. Air is too thin to provide enough lift to keep it up. 2. The engines breathe air and will not work if it is too thin. 3. The blackbird uses aerodynamic controls which have no effect once the air gets too thin. Has no rcs system. The shuttle needs to be that blunt to survive reentry. The blackbird is too aerodynamic, leaving the materials too thin to not fail during reentry. You are comparing 2 different vehicles with 2 different uses. Its like saying shipwrecks prove that submarines can't exist. Maybe do some research and understand the physics and engineering before making up your mind.