There's more lithium in Nevada, possibly double the amount of what is in Arkansas.
From what I'm reading online, the amount of lithium per vehicle batter pack is 8 - 14 kg. The lithium in Nevada (20 million metric tons, on the low-end) is only enough for 2.5 million cars.
I don't really read much about EV's because I think they suck. That being said, US consumers buy somewhere in the realm of 13,000,000 new cars, annually. It would seem that the world is going to be facing a massive lithium shortage. Solid state batteries also use lithium. Seems like the next generation of battery is going to need to evolve quite rapidly.