> Do you have some required reading to share here

Lenin's Imperialism

> but bad for economic growth

Yes, it is bad for economic growth, but this is not the tactic of protectionism. It is in the name that the purpose is to protect domestic production. It is done by forcing competition barriers on external producers

> What is the phase called?

Economic crisis / intense rivalry. US is economically threatened by the rise of China, it has been on the radar for many years. Things have reached a point where US can't just sit there and do nothing as China challenges the global status quo.

> What is this amputation and what spreading is it stopping?

The spreading is the slow but ongoing rise of Chinas economic power. The amputation is thr free-trade bariers