If we take QM seriously, there's nothing stopping it from affecting macroscopic events from a human perspective. A cannonball whose trajectory was planned in accordance with Newtonian physics could suddenly and unexpectedly move three feet to the left, it's just ridiculously unlikely.[0] This isn't a piecewise function where Newtonian physics is true within some constraints of speed and scale, Newtonian physics is simply wrong and useful.

[0]: Under the Everett interpretation, which is no more or less scientific than the Copenhagen interpretation, this happens all the time and is witnessed by many humans.