It’s not US West: San Francisco according to it’s DNS entry:
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-25.P1.el5_11.12 <<>> live.twitch.tv
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15514
;; flags: qr rd ra; QUERY: 1, ANSWER: 16, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;live.twitch.tv. IN A
;; ANSWER SECTION:
live.twitch.tv. 59 IN A 23.160.0.82
live.twitch.tv. 59 IN A 23.160.0.83
live.twitch.tv. 59 IN A 23.160.0.86
live.twitch.tv. 59 IN A 23.160.0.84
live.twitch.tv. 59 IN A 192.108.239.81
live.twitch.tv. 59 IN A 192.108.239.84
live.twitch.tv. 59 IN A 23.160.0.80
live.twitch.tv. 59 IN A 192.108.239.83
live.twitch.tv. 59 IN A 23.160.0.81
live.twitch.tv. 59 IN A 23.160.0.85
live.twitch.tv. 59 IN A 192.108.239.85
live.twitch.tv. 59 IN A 23.160.0.90
live.twitch.tv. 59 IN A 192.108.239.80
live.twitch.tv. 59 IN A 192.108.239.86
live.twitch.tv. 59 IN A 192.108.239.82
live.twitch.tv. 59 IN A 23.160.0.89
;; Query time: 46 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Jun 12 19:30:47 2017
;; MSG SIZE rcvd: 288
EDIT: Foot in mouth, made some incorrect assumptions. This is US West, San Francisco