Comcast, Illinois here.

You are not the only one. We hit some terrible nodes on our way to the California servers. We cannot avoid them, and this lag will happen every night between 8pm CST to about 11pm.

SE blames our ISP. Our ISP blames SE.

The only way this problem will be fixed is if the servers move to a more central location in NA. Otherwise, there is nothing anyone can do about it. It's downright sad.