Technically the ballon isn't moving itself in anyway at all, it instead is depending on the wind. As the atmospheric pressure lowers the maximum speed of the wind can increase greatly. For example the speed of the jet stream commonly exceeds 275 miles per hour. It looks like the strongest jet winds were closer to canada, had the jet been in the US it could have made it across the country in a day.
There was mention by the Chinese that is had some motive power of its own, or at least strongly implied when their PR said some the thing like “limited maneuvering capability”. That seems to indicate that it had some. It would a bit surprising if a payload the size of 2-3 school buses wasn’t outfitted with a reasonable amount of controllability, at least some control surfaces even if they inexplicably excluded even minimal and limited propulsion.
"Officials said the balloons are part of a fleet that China uses for surveillance, and they can be maneuvered remotely through small motors and propellers."
It doesn’t matter for the same reason that the earth doesn’t go flying out from under you if you jump into the air. Yes, it’s spinning, but so is everything else, so it nets to 0
The jetstream is fast enough that it factors into any flight at altitude when it comes to fuel estimations and path calculations, up to 12% difference or so iirc.
Indeed this is really obvious to anyone who regularly travels to California and back to the somewhere on the eastern half of the US (or vice versa). The time it takes for the east bound leg is way faster than the west bound leg. Going from San Francisco to Detroit for example is about an hour faster on the east bound direction.
