Im not sure i agree completely with this. What has made DIY CNC possible is the rapid improvement in electronics. Some of that stuff is still made in the USA. gecko comes to mind and is cost effective.
When i first got involved with CNC we where using Bandit controllers at work. Those controllers had a pretty large card rack and cost a good penny. Frankly an Arduino running GRBL leaves one with a similar level of performance.
Yes and what is worse our government promoted it with both political parties gladly profiting. Even now both political parties are not operating in the best interest if the American people.
American companies started buying from China to make more profits. China didn't steal manufacturing, we gave it to them.