KC is SEC in football now. In basketball, it's split between Mizzou and KU (not KSU), and tilts toward Mizzou.
And if you want to list big cities in each conference, the Big 12 is going to lose by a massive margin. The question in the future is (may?) be: how many people actually care? If that happens, Big 12 will close the gap some on the Pac as Pac fans aren't as hardcore. But for now, when it's simply about population, the Big 12 has little to hold up against the Pac. Pac just needs better management to turn its population into money. And Pac is far harder to pick apart because its bounded by a literal ocean on one side.