I’ve never been anywhere in the world as busy as some US corridors. It’s amazing to me how great the controllers are in New York. You have Newark, Kennedy, La Guardia, and teterboro all within a stones throw. I think there are some regional ATC differences for the environment... but it’s very spelled out on visual approaches, spacing, and TAs. That’s not the difference. SFO is also a busy airspace with OAK and SJC and a lot of GA. CX accepted the visual and they probably shouldn’t have. Tired. Long Duty... sun in the eyes. I’m not sure what happened. ATC and UA crews also interacted. It’s a lot of moving parts and not black and white. What’s missing is the visual from the cockpit. We don’t know what the crews saw or didn’t see. So all the speculation is worthless.