The term "protected computer" is defined in the CFAA act[1].

Basically its any computer used by a bank, the federal government, or used in interstate commerce.

This is just a quirk of the US system of government. If it doesn't fit those criteria, its going to be up to the state to prosecute based on the state's own version of the cfaa.

[1] https://www.law.cornell.edu/definitions/uscode.php?width=840...