Hmm? Highway means "public road" (and sometimes private) pretty much everywhere, legally, since before the US existed.

https://www.law.cornell.edu/wex/highways_and_motor_vehicles

https://en.m.wikipedia.org/wiki/Highway

"Freeway" is the term for the kind of road that has "highway" in its official name. Also "parkway", from the era when there was more landscaping around freeways.