USA via SFO
UniFoxOs:
I travel regularly to the US West Coast. If you enter the US at SFO, I think you'll find the experience OK. There can be queues at immigration, but they really try to get you through. I would, from past experience, avoid LAX.
And the Bay Area is a great introduction to California.
BA have two flights a day to SFO, Virgin have 1 and United have 1. BA and Virgin are 744s. I think United may be a 777.