Will a live USB for a Mac run on a chromebook or windows computer?
No, the disk should still be able to boot.

There isn't actually a difference between the operating system in the .img and .iso. They're just different ways of storing the same information. 

Kali(or any other *nix) distro is an operating system, just as Windows and OS X are. Whether or not an operating system will run on a computer is solely dependent on the hardware, not the software already on the computer.