No they are not. What do you think why the Belt Road Initiative exists? In my opinion it's mostly to get Africa up to speed, similar to the post WW2 marshall plan, so that African demand can fill the gaps that Europe/Africa leave.

Also, China has massive sums of dollars and euros, they can simply play the "long game", i.e. weather out the storm until Europe/US caves.

Yeah that's not how it works at all thanks to globalisation. About 10 other countries will step in to provide all the cheap widgets in Chinas place about 3 seconds after they 'cut us off'

Which countries have anything even remotely matching the supply chain of Shenzen built up and trained - and with the spare capacity available?

Many companies are moving out of China at the moment, either due to the threat of a Trump-caused trade war or because other countries are even cheaper than China, and it takes them years.

China can weather one year of export blockade to EU/US. No problem. But EU/US can not, not in any way.