I am travelling to San Francisco from the UK soon. I have been told that the waiting in line at security and immigration at major airports is currently horrendous.
Would I be better off travelling via Pittsburgh or Charlotte (which will also save me $100)so that I can enter there; or should I bite the bullet and go direct to San Francisco?
Thanks for any suggestions, Greybeard

Just go direct to SF. The line in SF could not possibly add more time to your trip than the plane change, plus you'd have the added anxiety of making a connection.

Go direct to SF. I was stuck at US Immigration last year for 90 minutes in Charlotte and missed a connection!

Go non-stop to SFO. The one-stop would save $100 but would cost you 4 hours extra, maybe more. If you fly non-stop then you won't have to worry about the weather in PIT or CLT.

The flight time between Charlotte and SFO would be four hours plus the time you would spend de-boarding, collecting luggage, customs, rechecking luggage, waiting on plane, reboarding, yadda, yadda. This would add at least 6 hours to your trip at the very least.

In general you're better off at the larger airports - even though the lines look enormous they usually have many more agents working so the lines move more quickly. The only time this doesn't work is if weather causes a huge # of planes to land at once - and I don;t know how to determine this in advance.

I was just at the San Francisco International Terminal this last weekend, seeing someone off.

The International Terminal opened recently, is large, and looks to be very efficient. From the looks of it, coming in and checking through customs and immigration will be a breeze as compared to some of the older airports on the East Coast - thinking of my nightmare entry at Philadelphia last year!

Another vote for flying directly into SFO.

I arrived at LAX on Jan 2 from London on a completely full United flight. At immigration, there were at least twice as many agents processing non-citizens as there were working with US citizens. The numbver of passengers in each line was about the same. It seemed that most passengers,if not all, including non-citizens, got to the carousel before the luggage.