Kansas City and Sacramento are about 1,444 miles apart by road. Split the difference and you arrive near Denver, the city closest to the halfway point between them. That puts roughly 11 hr 41 min of driving on the Kansas City side and 18 hr 35 min on the Sacramento side — the fairest single meeting point among the cities near the middle.
Over this distance most people will fly rather than drive the whole way. Denver still makes a fair, central place for Kansas City and Sacramento to converge, splitting the travel instead of asking one side to cross the country.
If Denver doesn't have what you're after, Salt Lake City and Albuquerque are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Kansas City and Sacramento.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.