0 - The reasons are due to maximum allowable pressures, and barrel rifling. At max pressure for a 40gr bullet you’re going to get maybe Mach 1.1, maybe. If you want to go faster without increasing pressure above spec, the solution is a lighter bullet. But lighter bullets often like different rifling, and virtually all off the shelf 22lr barrels come with 1:16 rifling, unsuitable for extra light bullets. Also, lighter bullet get pushed around by the wind more; you’d often rather compensate for more drop than wind, since drop is more predictable.
Specifically CIP sets the maximum pressure of 22lr at 24,646 psi. An extremely high number considering, but pretty pedestrian compared to other cartridges. For example NATO sets a maximum pressure of 62,366 psi for its primary rifle caliber, 5.56x45mm. It’s genuinely amazing that rifle barrels don’t regularly explode, to be honest.
In transonic flight, some parts of the airflow are starting to become supersonic, and compressibility starts to become a factor. Something called "wave drag" is important in this regime, as the compression wave is moving along with the aircraft.
In supersonic flow, compressibility of the air becomes the main thing and the flow is defined by the positions of the various shock waves. Ramjet engines work in this regime (the aircraft is moving fast enough that the forward movement is enough to compress the incoming air to the engine, without compressor blades). In a conventional ramjet engine, the flow within the engine is subsonic (the compressed air, being more dense, moves more slowly within the engine), so combustion works the usual way.
In hypersonic flow, temperatures are getting very high (air is heated by compression). Scramjet engines become a thing (the "SC" is for supersonic combustion: air flowing through the combustion stage at supersonic speed).