We flew in two days ago, flying on United HKG - SFO - SAN with a 2 hour layover in SFO. We arrived at SFO slightly early at 8.30am, and saw a huge crowd in the room. The lines snaked around and back the automatic scanners and round all parts of the room. In the end took 2+ hours to get to and through customs. By the time we'd located our bags (they'd been moved away from the carousel) it was close to 11, by which time our San Diego flight, though slightly delayed, had taken off. We exited international and found the United desk just to the left. Before we got there a baggage guy scanned our bags and said he could see we'd already been rebooked onto a flight at 1pm and to make our way over to Terminal 3, yay! I was relieved to only lose 2 hours.
But when we got to Terminal 3 and I scanned our boarding passes nothing worked. It wasn't at all clear where to go, I sent my wife to the additional information counter which had about 10 people in queue, while I was directed by a baggage guy to another lady at a desk who was helping a few people. She seemed stuck with one group for 40 minutes. In the end we both waited in our respective queues for exactly an hour. Finally we got to talk to someone that could at least help us. He said the 1pm was overbooked, he had no idea why we'd been told we were booked on it because we weren't. My heart sank as he said the 4pm was likewise fully booked and the earliest he could put us on was 6.15pm. Having no choice we booked that flight and waited in SFO terminal 3 for 6 hours. In the end it wasn't too bad as they had comfy seats and we just slept for most it.
Still I would not like to repeat that experience. I had heard all this time that SFO was the better option to transit through than LAX but I'm wondering is that still the case? I'd been to LAX last October and it was reasonably smooth, although I've never had to clear customs at LAX. Is SFO or LAX worse for customs? And if flying to SAN from the Asia-Pacific which would you choose to transit in?
(PS On the return leg I'm worried since we only have a 1 hour layover at SFO, granted we won't have to pass customs and security but I'm thinking about getting to San Diego airport early to see if there's an earlier flight available.)