UA 900 from SFO will almost certainly arrive at Concourse C in Terminal 1. I can't remember a time when UA arrived or departed anywhere else. Your LH flight to Birmingham (BHX) will generally leave from Concourse B or the upper level of Concourse A in Terminal 1. If your LH flight leaves from Concourse B, you will have a 10-minute walk; if Concourse A, a 10-minute walk plus a short ride on the Sky Train, which adds a 5-minute wait. Either way, if you are careful to follow the signs to your concourse and gate , you will stay airside in the "non-Schengen" area, and you won't have to clear either Security or Immigration. So, I think your 65 minutes connection is doable. Of course, if UA 900 is late, all bets are off!