Better have a plan for charging b/w STL and KC as well. There's not really anything in Columbia yet. You'll just need an hour or two on J1772 to make it to KC. Since you don't have twin chargers you're gonna be in a bit of a crunch. There is now a HPWC at the St.Louis service center and a few friendly Tesla owners there that often offer their HPWC. KC has several J1772 chargers, a couple at hotels, so if you get that far in your first day you could spend the night and get topped up before embarking on the final leg.
First: have you taken your car out for any kind of long-distance drive yet?
Either using Superchargers, or using L2 charging.
I concur with Rifleman: you would be better taking the longer distance, but actually quicker time, by sticking to the Supercharger route thru South Dakota.
Maybe on the way back you try the more direct route (thru KC and StL), but you will dread having to stop and charge during the day, at either a J1772 outlet, or a NEMA 14-50 at an RV park (faster of those two).
For overnight charging (while you sleep), it is not that big of a deal to use the J1772 or 14-50, but it is not the premium use of one's time to charge that way during daylight hours.
And efusco is correct also.
You will not be able to make it from StL to KC without an intermediate charge somewhere. And you will probably need a supplemental charge from KC to Salinas.
Skipping from Supercharger to Supercharger is fast, because you are generally not worried about running out of range, and your speed can be a bit faster.
Going from L2 to L2 requires a bit more restraint to keep your range (and buffer) numbers up.