It is a myth. America is still the top manufacturer in the world.
The difference is that China makes tons of duplicate copies of cheap goods, while America makes high value, lower run, complicated goods.
Which is why if you look only at consumer good you get the mistaken assumption that manufacturing is leaving the US. Try sourcing $100,000 machines and all of them are made in the US.
The "myth" claimed by the OP was that manufacturers have left the US. That is not a myth despite the US remaining a top manufacturing country - because, as you say, what remained specialized, high-value items (planes, chemicals).
A large number of particular manufacturers left the US.
The difference is that China makes tons of duplicate copies of cheap goods, while America makes high value, lower run, complicated goods.
Which is why if you look only at consumer good you get the mistaken assumption that manufacturing is leaving the US. Try sourcing $100,000 machines and all of them are made in the US.