I've not seen one for batteries yet but there's a few in-depth looks at what contributed to price declined of PV solar historically and consistent, long term government support and scale up are the big factors.

When something is consistently reducing in cost by 90% in a decade, there's just not that much room for labour (slave or otherwise) to be a big part of the answer (expect as an inefficiency to be avoided).

Would you invest billions in the USA to build something that Donald Trump is having a culture war about? That uncertainty is enough to kill investment and send it overseas and add to someone else's momentum. (And someone was confused the other day why China would be on twitter trying to get Donald Trump elected, because he's such a meanie towards them).

Battery manufacturing is automated.