Riot: "Hey guys, we know servers have been sucking lately, but we finally managed to confirm things so that we can solve this issue long-term, versus spending money to fix it short term."
Idiots: "But we want the short term fix now because we lack the ability to think ahead!"
They are dealing with the issue. Shit takes time in the real world, bro, especially large problems like server issues.
Also, South Korea is smaller than California, and all of China's infrastructure is basically in one place. The US has neither of those luxuries, it's more expensive than you can imagine to lay the infrastructure over large distances. Guess what? Riot's trying to do that, just to solve lag issues in the States. Try to wrap your head around the fact that they're basically building a nationwide wired network from scratch for their game.