In the meantime, the Liberty phone seems to be the closest option for a US-made smartphone. While not entirely comprised of US-sourced components, the PCBs are manufactured in California, as well as device packaging and assembly.
April 10 update: Right on time, the author of the OP’s linked article has now published an article on the Liberty phone.
Linux has been ready for some time within various educational programs, but maybe you are referring to relatively early education curriculum in public schools? The general anecdotes I’ve heard from teachers within a variety of grade levels in the USA (mostly elementary and high school levels, but some doctoral engineering/scientific as well) convey that the largest hurdles to overcome are: