Philippe Fabre
Agronomist. Seed specialist. Working in Asia for 30+ years.1y
What would happen if America completely cut China out and sanctioned them like North Korea?
Assuming that China would retaliate immediately by cutting the USA out, let’s see what would happen:

China-held US Treasury: If the US cancel them, they will pay them back + hefty compensations to China. Or force China to sell them to investors. With a loss. Not a huge problem for either one.
China will lose $500 billion export sales to the US. A big impact on China industry and jobs. Very BAD for China.
The US will lose $150 billion sales to China. Thousands of farmers will go bankrupt. Very BAD for the US.
The US will lose $600 billion FAS in China. Foreign Affiliated Sales in China by US companies, produced outside USA. Very BAD for the US.
The US will size Chinese investments in the US. Around $ 200 billion. Mostly in real estate. BAD for China.
China will size US investments in China. Around $ 2 Trillion. Mostly factories. Very BAD for the US.
If an actual war is avoided, the world would eventually be divided in 2: The USA trade zone and the China trade zone. No doubt Oceania and Latin America will side with the US. Asia and Africa will side with China. Europe will be under huge pressure from both sides. Since it all started from an irrational decision from the US, Europe + Russia are more likely to side with China. Except the UK, of course!
Overall, a very bad deal for the two sides. Worse for the US.
But that will not happen! NEVER!

Even in his worst fit of rage ever, Trump would never decide that. Everybody will discourage him. And if he still insists, the GOP will drop their support. The 25th might be organized. Or some kind of bi-partisan congress revolt against the crazy dictator.