There technically is no a country-wide legislation in the US, but Michigan has it, and some other states have similar requirements:

And only for regular cars, there is no right to repair for commercial vehicles: https://en.wikipedia.org/wiki/Motor_Vehicle_Owners%27_Right_...

There are also long-standing legal requirements for automakers to be separate from car dealers, which also translate into making the repair/diagnostics equipment available.

yes. the same law (or, rather, the movement at the time within congress) is what standardized the OBD-II connector and mandated its inclusion in all cars from 1996(?) onwards: the idea that consumers should be able to repair their own big-ticket items should they choose to.