Speed of sound at sea level is about 740 mph and change. It actually drops with altitude (less dense air). In order to be going 12,000 to 15,000 mph yet be subsonic you'd have to be travelling through a very dense material with a very high speed of sound. Something like glass or aluminum. I don't think we're likely to be "flying" through solid aluminum anytime soon. Maybe when we do that whole warp-drive thing.
Biden is falling apart. His mind has got to be a bag of squirrels with rabies.