I doubt if you will make your domestic flight. You should re book a domestic flight departing at least 2 hours after SQ2 is set to arrive.

You indicate you are set to arrive SFO at 1925 and the domestic flight leaves at 8PM, that's only 35 minuets to connect.

In addition to having to clear ICE at SFO, after immagration but before clearing customs, the luggage needs to arrive off of the SQ flight. You will leave this area with your baggage. After you clear customs with your bags, you will need to deliver the bags just outside of the arrival area to the baggage agent for transport to the domestic connection. Sometimes there is a line to re check the bags. Then you need to walk to the domestic terminal. UA is adjacent to the international terminal but AS is a bit longer walk. Then you need to clear the domestic security. I have arrived on SQ 2 in 1st and was one of the 1st passengers off the flight. When I got to the UA terminal the lines at security were outrageously long. Fortunately my domestic flight was departing 2.5 hours after SQ2 arrived.

Re book the domestic flight and eliminate the stress and enjoy your journey.