Apple has designed many of the assembly techniques and tools used in their devices. Almost all of it is proprietary and secret but Apple did notoriously share its recycling robot:
To my point, this robot is actually in the US (Texas) because robotics enable lower labour, making it an affordable operation in North America. This materials mining stage is one instance where Apple can viably bring iPhone manufacturing to the US. Chip manufacturing is another. But componentry and final assembly are nowhere in sight, unless Apple invents an assembly robot unlike anything that exists today.