You don't need that much of foreign mined materials. The continental US has a bunch of really large lithium reserves, with Thacker Pass being supposed to be able to deliver 25% of the world's output in the end [1], and new sodium based chemistries? All they need is table salt, available for effectively free from the brine of California's desalination plants.

[1] https://en.wikipedia.org/wiki/Thacker_Pass_lithium_mine